American Home Mortgage Investment Corp.

Exhibit 1.1

Execution Version

American Home Mortgage Investment Corp.

4,000,000 Shares ¹

Common Stock

($0.01 par value)

Underwriting Agreement

New York, New York

April 30, 2007

Citigroup Global Markets Inc.

As Representative of the Underwriters,

c/o Citigroup Global Markets Inc.

388 Greenwich Street

New York, New York 10013

Ladies and Gentlemen:

American Home Mortgage Investment Corp., a corporation organized under the laws of Maryland (the “Company”), proposes to sell to the several underwriters named in Schedule II hereto (the “Underwriters”), for whom you (the “Representatives”) are acting as representatives, the number of shares of common stock, $0.01 par value (“Common Stock”), of the Company set forth in Schedule I hereto (the “Securities”) (said shares to be issued and sold by the Company being hereinafter called the “Underwritten Securities”). The Company also proposes to grant to the Underwriters an option to purchase up to the number of additional shares of Common Stock set forth in Schedule I hereto to cover over-allotments, if any (the “Option Securities”; the Option Securities, together with the Underwritten Securities, being hereinafter called the “Securities”). To the extent there are no additional Underwriters listed on Schedule I other than you, the term Representatives as used herein shall mean you, as Underwriters, and the terms Representatives and Underwriters shall mean either the singular or plural as the context requires. Any reference herein to the Registration Statement, the Base Prospectus, any Preliminary Prospectus or the Final Prospectus shall be deemed to refer to and include the documents incorporated by reference therein pursuant to Item 12 of Form S-3 which were filed under the Exchange Act on or before the Effective Date of the Registration Statement or the issue date of the Base Prospectus, any Preliminary Prospectus or the Final Prospectus, as the case may be; and any reference herein to the terms “amend,” “amendment” or “supplement” with respect to the Registration Statement, the Base Prospectus, any Preliminary Prospectus or the Final Prospectus shall be deemed to refer to and include the filing of any document under the Act

or the Exchange Act, as the case may be, after the Effective Date of the Registration Statement or the issue date of the Base Prospectus, any Preliminary Prospectus or the Final Prospectus, as the case may be, deemed to be incorporated therein by reference. Certain terms used herein are defined in Section 20 hereof.

1. Representations and Warranties. The Company represents and warrants to, and agrees with, the Underwriters as set forth below in this Section 1.

(a) The Company meets the requirements for use of Form S-3 under the Act and has prepared and filed with the Commission a registration statement (the file number of which is set forth in Schedule I hereto) on Form S-3, including a related Base Prospectus, for registration under the Act of the offering and sale of the Securities. Such Registration Statement, including any amendments thereto filed prior to the Execution Time, have become effective. The Company may have filed with the Commission, as part of an amendment to the Registration Statement or pursuant to Rule 424(b), one or more preliminary prospectus supplements relating to the Securities, each of which has previously been furnished to you. The Company will file with the Commission a final prospectus supplement relating to the Securities in accordance with Rule 424(b). As filed, such final prospectus supplement shall contain all information required by the Act and the rules thereunder, and, except to the extent the Representatives shall agree in writing to a modification, shall be in all substantive respects in the form furnished to you prior to the Execution Time or, to the extent not completed at the Execution Time, shall contain only such specific additional information and other changes (beyond that contained in the Base Prospectus and any Preliminary Prospectus) as the Company has advised you, prior to the Execution Time, will be included or made therein. The Registration Statement, at the Execution Time, meets the requirements set forth in Rule 415(a)(1)(x).

(b) On each Effective Date, the Registration Statement did, and when the Final Prospectus is first filed in accordance with Rule 424(b) and on the Closing Date (as defined herein) and on any date on which Option Securities are purchased, if such date is not the Closing Date (a “settlement date”), the Final Prospectus (and any supplement thereto) will, comply in all material respects with the applicable requirements of the Act and the Exchange Act and the respective rules thereunder; on each Effective Date and at the Execution Time, the Registration Statement did not and will not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein not misleading; and on the date of any filing pursuant to Rule 424(b) and on the Closing Date and any settlement date, the Final Prospectus (together with any supplement thereto) will not include any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading; provided, however, that the Company makes no representations or warranties as to the information contained in or omitted from the Registration Statement or the Final Prospectus (or any supplement thereto) in reliance upon and in conformity with information furnished in writing to the Company by or on behalf of any Underwriters through the Representatives specifically for inclusion in the Registration Statement or the Final Prospectus (or any supplement thereto), it being understood and agreed that the only such information furnished by or on behalf of any Underwriters consists of the information described as such in Section 8 hereof.

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(c) (i) The Disclosure Package does not contain any untrue statement of a material fact or omit to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading. The preceding sentence does not apply to statements in or omissions from the Disclosure Package based upon and in conformity with written information furnished to the Company by any Underwriters through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of any Underwriters consists of the information described as such in Section 8 hereof. The documents incorporated by reference in any Preliminary Prospectus or the Final Prospectus conformed, and any further documents so incorporated will conform, when filed with the Commission, in all material respects to the requirements of the Exchange Act or the Securities Act, as applicable, and the rules and regulations of the Commission thereunder.

(d) (i) At the time of the most recent amendment to the Registration Statement for the purposes of complying with Section 10(a)(3) of the Act (whether such amendment was by post-effective amendment, incorporated report filed pursuant to Sections 13 or 15(d) of the Exchange Act or form of prospectus), (ii) at the time the Company or any person acting on its behalf (within the meaning, for this clause only, of Rule 163(c)) made any offer relating to the Securities in reliance on the exemption in Rule 163, and (iii) at the Execution Time (with such date being used as the determination date for purposes of this clause (iii)), the Company was or is (as the case may be) a “well-known seasoned issuer” as defined in Rule 405. The Company has been, since the time of initial filing of the Registration Statement and continues to be, eligible to use Form S-3 for the offering of the Shares.

(e) (i) At the earliest time after the filing of the Registration Statement that the Company or another offering participant made a bona fide offer (within the meaning of Rule 164(h)(2)) of the Securities and (ii) as of the Execution Time (with such date being used as the determination date for purposes of this clause (ii)), the Company was not and is not an Ineligible Issuer (as defined in Rule 405), without taking account of any determination by the Commission pursuant to Rule 405 that it is not necessary that the Company be considered an Ineligible Issuer.

(f) Each Issuer Free Writing Prospectus, if any, do not include any information that conflicts with the information contained in the Registration Statement, including any document incorporated therein by reference and any prospectus supplement deemed to be a part thereof that has not been superseded or modified. The foregoing sentence does not apply to statements in or omissions from any Issuer Free Writing Prospectus based upon and in conformity with written information furnished to the Company by the Underwriters through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of any Underwriters consists of the information described as such in Section 8 hereof.

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(g) the Company has an authorized and outstanding capitalization as set forth in the Disclosure Package and Final Prospectus under the caption “Capitalization;” the outstanding shares of capital stock of the Company and its subsidiaries (as defined below) have been duly and validly authorized and issued and are fully paid and non-assessable and were not issued in violation of any preemptive right, resale right, right of first refusal or similar right, and all of the outstanding shares of capital stock of the subsidiaries are directly or indirectly owned of record and beneficially by the Company; except as disclosed in the Disclosure Package and Final Prospectus, there are no outstanding (i) securities or obligations of the Company or any of its subsidiaries convertible into or exchangeable for any capital stock of the Company or any such subsidiary, (ii) warrants, rights or options to subscribe for or purchase from the Company or any such subsidiary any such capital stock or any such convertible or exchangeable securities or obligations, or (iii) obligations of the Company or any such subsidiary to issue any shares of capital stock, any such convertible or exchangeable securities or obligation, or any such warrants, rights or options;

(h) each of the Company and the Company’s subsidiaries has been duly incorporated and is validly existing as a corporation or limited liability company in good standing under the laws of its respective jurisdiction of incorporation or organization with full corporate or limited liability company power and authority, as the case may be, to own its respective properties and to conduct its respective business as described in the Disclosure Package and the Final Prospectus and, in the case of the Company, to execute and deliver this Agreement and to consummate the transactions contemplated hereby; complete and correct copies of the articles of incorporation, charter or organizational documents, as applicable, and of the bylaws, and all amendments and supplements thereto (collectively, “Charter Documents”), of the Company and the subsidiaries have been delivered to the Representatives, and except as set forth in the exhibits to the Registration Statement no changes therein will be made subsequent to the date hereof and prior to the Closing Date or, if later, each settlement date;

(i) the Company and each of the subsidiaries are duly qualified in or licensed by each jurisdiction in which they conduct their respective businesses, and the Company and each of the subsidiaries are duly qualified, and are in good standing, in each jurisdiction in which they own or lease real property or maintain an office and in which such qualification is necessary, except where the failure to be so qualified or licensed and in good standing, individually and in the aggregate, would not have a material adverse effect on the assets, business, operations, earnings, prospects, properties or condition (financial or otherwise) of the Company and its subsidiaries taken as a whole whether or not arising from transactions occurring in the ordinary course of business (a “Material Adverse Effect”); except as disclosed in the Disclosure Package or Final Prospectus, no subsidiary is prohibited or restricted, directly or indirectly, from paying dividends to the Company, or from making any other distribution with respect to such subsidiary’s capital stock or from repaying to the Company or any other subsidiary any amounts which may from time to time become due under any loans or advances to such subsidiary from the Company or such other subsidiary, or from transferring any such subsidiary’s property or assets to the Company or to any other subsidiary; other than as disclosed in the Disclosure Package or Final Prospectus, the Company does not own, directly or indirectly, any capital stock or other equity securities of any other corporation or any ownership interest in any partnership, joint venture or other association;

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(j) the Company and its subsidiaries are in compliance in all material respects with all applicable laws, rules, regulations, orders, decrees and judgments, including those relating to transactions with affiliates;

(k) neither the Company nor any of its subsidiaries is in breach of or in default under (nor has any event occurred which with notice, lapse of time, or both would constitute a breach of, or default under), its respective Charter Documents, or in the performance or observance of any covenant contained in any license, indenture, mortgage, loan or credit agreement to which the Company or any of its subsidiaries is a party or by which any of them or their respective properties is bound, except for such breaches or defaults which, individually and in the aggregate, would not have a Material Adverse Effect, and the execution, delivery and performance of this Agreement, consummation of the transactions contemplated hereby (including the issuance and sale of the Securities) and the application of the net proceeds from the offering and sale of the Securities to be sold by the Company in the manner set forth in the Disclosure Package and Final Prospectus under the caption “Use of Proceeds” will not (A) conflict with, or result in any breach of, or constitute a default under (nor constitute any event which with notice, lapse of time, or both would constitute a breach of, or default under), (i) any provision of the Charter Documents of the Company or any of its subsidiaries, (ii) any provision of any license, indenture, mortgage, loan or credit agreement or other agreement or instrument to which the Company or any of its subsidiaries is a party or by which any of them or their respective properties may be bound or affected, or (iii) any federal, state, local or foreign law, regulation or rule or any decree, judgment or order applicable to the Company or any of its subsidiaries, except in the case of clauses (ii) or (iii) for such breaches or defaults which, individually and in the aggregate, would not have a Material Adverse Effect or (B) result in the creation or imposition of any lien, charge, claim or encumbrance (collectively, “Lien”) upon any property or asset of the Company or its subsidiaries, except for such Liens which, individually and in the aggregate, would not have a Material Adverse Effect;

(l) all necessary corporate action has been duly and validly taken by the Company to authorize the issuance and sale of the Securities by the Company; the execution and delivery of this Agreement has been duly authorized by the Company and this Agreement is a legal, valid and binding agreement of the Company, enforceable in accordance with its terms, except as such enforceability may be limited by bankruptcy, insolvency, reorganization, moratorium or similar laws affecting creditors’ rights generally, and by general principles of equity, and except to the extent that the indemnification and contribution provisions of Section 8 hereof may be limited by federal or state securities laws and public policy considerations in respect thereof;

(m) no approval, authorization, consent or order of or filing with any federal, state or local governmental or regulatory commission, board, body, authority or agency is required in connection with the Company’s execution, delivery and performance of this Agreement, its consummation of the transaction contemplated hereby, and its issuance,

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sale and delivery of the Securities, other than (A) such as have been obtained, or will have been obtained at the Closing Date or each settlement date, as the case may be, under the Act, (B) such approvals as have been obtained in connection with the approval of the listing of the Securities on the New York Stock Exchange and (C) any necessary qualification under the securities or blue sky laws of the various jurisdictions in which the Securities are being offered by the Underwriters;

(n) each of the Company and its subsidiaries has all necessary licenses, authorizations, consents and approvals and has made all necessary filings required under any federal, state or local law, regulation or rule, and has obtained all necessary authorizations, consents and approvals from other persons, required in order to conduct their respective businesses as described in the Disclosure Package and Final Prospectus, except to the extent that any failure to have any such licenses, authorizations, consents or approvals, to make any such filings or to obtain any such authorizations, consents or approvals would not, individually and in the aggregate, have a Material Adverse Effect; neither the Company nor any of its subsidiaries is in violation of, in default under, or has received any notice regarding a possible violation, default or revocation of any such license, authorization, consent or approval or any federal, state, local or foreign law, regulation or rule or any decree, order or judgment applicable to the Company or any of its subsidiaries the effect of which, individually or in the aggregate, would reasonably be expected to result in a Material Adverse Effect;

(o) there are no actions, suits, proceedings, inquiries or investigations pending or, to the knowledge of the Company, threatened against the Company or any of its subsidiaries or any of their respective officers and directors or to which the properties, assets or rights of any such entity are subject, at law or in equity, before or by any federal, state, local or foreign governmental or regulatory commission, board, body, authority, arbitral panel or agency which could result in a judgment, decree, award or order having a Material Adverse Effect or preventing the consummation of the transactions contemplated hereby;

(p) the financial statements, including the notes thereto, included or incorporated by reference in the Disclosure Package and the Final Prospectus present fairly in all material respects the consolidated financial position of the entities to which such financial statements relate (the “Covered Entities”) as of the dates indicated and the consolidated results of operations and changes in financial position and cash flows of the Covered Entities for the periods specified; such financial statements have been prepared in conformity with United States generally accepted accounting principles applied on a consistent basis during the periods involved and in accordance with Regulation S-X promulgated by the Commission; the financial statement schedules included or incorporated by reference in the Registration Statement fairly present the information shown therein; the unaudited pro forma financial information (including the related notes) included or incorporated by reference in the Disclosure Package and Final Prospectus or any Preliminary Prospectus complies as to form in all material respects to the applicable accounting requirements of the Act and the rules and regulations thereunder, and management of the Company believes that the assumptions underlying the pro forma adjustments are reasonable; such pro forma adjustments have been properly

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applied to the historical amounts in the compilation of the information and such information fairly presents with respect to the Company and the subsidiaries, the financial position, results of operations and other information purported to be shown therein at the respective dates and for the respective periods specified;

(q) Deloitte & Touche LLP whose reports on the consolidated financial statements of the Company and its subsidiaries are filed with the Commission and incorporated by reference in the Registration Statement, Disclosure Package and Final Prospectus, are and were during the periods covered by their reports independent public accountants as required by the Act and the regulations thereunder;

(r) the capital stock of the Company conforms in all material respects to the description thereof contained in the Registration Statement, Disclosure Package and the Final Prospectus;

(s) the Securities have been duly authorized and, when issued and duly delivered against payment therefor as contemplated by this Agreement, will be validly issued, fully paid and nonassessable, free and clear of any pledge, Lien, security interest or other claim, and the issuance and sale of the Securities by the Company is not subject to preemptive or other similar rights arising by operation of law, under the Charter Documents of the Company, under any agreement to which the Company or any of its subsidiaries is a party or otherwise;

(t) neither the Company nor any of its affiliates (i) is required to register as a “broker” or “dealer” in accordance with the provisions of the Exchange Act, or the rules and regulations thereunder, or (ii) directly, or indirectly through one or more intermediaries, controls or has any other association with (within the meaning of Article I of the Bylaws of the National Association of Securities Dealers, Inc. (the “NASD”)) any member firm of the NASD;

(u) the form of certificate used to evidence the Common Stock complies in all material respects with all applicable statutory requirements and any requirements under the Company’s certificate of incorporation;

(v) the Company has good and marketable title in fee simple to its office headquarters, free and clear of all Liens, except for such Liens or defects in title which would not individually and in the aggregate have a Material Adverse Effect; and any real property and buildings held under lease by the Company or any subsidiary are held under valid, existing and enforceable leases, except for any exceptions which would not individually and in the aggregate have a Material Adverse Effect;

(w) the Company and each of its subsidiaries have in place a system of internal accounting controls sufficient to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles and including those policies and procedures that (i) pertain to the maintenance of records that in reasonable detail accurately and fairly reflect the transactions and dispositions of the assets of the

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Company, (ii) provide reasonable assurance that transactions are recorded as necessary to permit the preparation of the Company’s consolidated financial statements in accordance with generally accepted accounting principles, (iii) provide reasonable assurance that receipts and expenditures of the Company are being made only in accordance with management’s general or specific authorization, and (iv) provide reasonable assurance regarding prevention or timely detection of unauthorized acquisition, use or disposition of the Company’s assets that could have a material effect on its financial statements;

(x) each of the Company and the subsidiaries has filed on a timely basis all necessary federal, state, local and foreign income and franchise tax returns required to be filed through the date hereof and have paid all taxes shown as due thereon; and no tax deficiency has been asserted against any such entity, nor does any such entity know of any tax deficiency which is likely to be asserted against any such entity which, if determined adversely to any such entity, could, individually or in the aggregate, have a Material Adverse Effect; all tax liabilities are adequately provided for on the respective books of such entities;

(y) neither the Company nor any of its subsidiaries nor, to the knowledge of the senior executive officer’s of the Company, any officer or director purporting to act on behalf of the Company or any of its subsidiaries has at any time: (i) made any contributions to any candidate for political office, or failed to disclose fully any such contributions, in violation of law, (ii) made any payment to any state, federal or foreign governmental officer or official, or other person charged with similar public or quasi-public duties, other than payments required or allowed by applicable law, (iii) made any payment outside the ordinary course of business to any investment officer or loan broker or person charged with similar duties of any entity to which the Company or any of its subsidiaries sells or from which the Company or any of its subsidiaries buys loans or servicing arrangements for the purpose of influencing such agent, officer, broker or person to buy loans or servicing arrangements from or sell loans to the Company or any of its subsidiaries, (iv) engaged in any transactions, maintained any bank account or used any corporate funds except for transactions, bank accounts and funds which have been and are reflected in the normally maintained books and records of the Company and its subsidiaries or (v) made any other payment of funds of the Company or its subsidiaries or received or retained any funds in violation of any law, rule or regulation, which payment, receipt or retention of funds is of a character required to be disclosed in the Registration Statement, Disclosure Package or the Prospectus;

(z) the Company acknowledges and agrees that (i) the Underwriters are acting as a principal and not as an agent or fiduciary of the Company and (ii) its engagement of the Underwriters in connection with the offering of the Securities contemplated hereby and not in any other capacity; none of the Underwriters, their representatives or their legal counsel is advising or has advised the Company, its affiliates or any other person as to any legal, tax, investment, accounting, financial or regulatory matters in any jurisdiction with respect to the transactions contemplated hereby; the Company shall consult with its own advisors concerning such matters and agrees that it is solely responsible for making its own judgments in connection with the offering of the Securities contemplated hereby (irrespective of whether the Underwriters have advised or are currently advising the Company on related or other matters);

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(aa) the Company has not distributed and will not distribute any Prospectus or other offering material in connection with the offer and sale of the Securities;

(bb) neither the Company nor any of the subsidiaries is and, after giving effect to the offering and sale of the Securities, will be an “investment company” or an entity “controlled” by an “investment company”, as such terms are defined in the Investment Company Act of 1940, as amended (the “Investment Company Act”);

(cc) the Company meets the requirements for qualification and taxation as a “real estate investment trust” (a “REIT”) under the Internal Revenue Code of 1986, as amended (the “Code”); and

(dd) as of the date of this Agreement and as of the date of the filing of the Company’s report on Form 10-K for the year ended December 31, 2006, the Company meets the requirements for use of Form S-3 pursuant to the standards for such form prior to October 21, 1992.

Any certificate signed by any officer of the Company and delivered to the Representatives or counsel for the Underwriters in connection with the offering of the Securities shall be deemed a representation and warranty by the Company, as to matters covered thereby, to each Underwriter.

2. Purchase and Sale. (a) Subject to the terms and conditions and in reliance upon the representations and warranties herein set forth, the Company agrees to sell to each Underwriter, and each Underwriter agrees, severally and not jointly, to purchase from the Company, at the purchase price set forth in Schedule I hereto, the number of Underwritten Securities set forth opposite such Underwriter’s name in Schedule II hereto.

(b) Subject to the terms and conditions and in reliance upon the representations and warranties herein set forth, the Company hereby grants an option to the Underwriters to purchase, severally and not jointly, up to the number of Option Securities set forth in Schedule I hereto at the same purchase price per share as the Underwriters shall pay for the Underwritten Securities. Said option may be exercised only to cover over-allotments in the sale of the Underwritten Securities by the Underwriters. Said option may be exercised in whole or in part at any time on or before the 30th day after the date of the Final Prospectus upon written or telegraphic notice by the Representatives to the Company setting forth the number of Option Securities as to which the several Underwriters are exercising the option and the settlement date. The number of Option Securities to be purchased by each Underwriter shall be the same percentage of the total number of Option Securities to be purchased by the several Underwriters as such Underwriters is purchasing of the Underwritten Securities, subject to such adjustments as you in your absolute discretion shall make to eliminate any fractional shares.

3. Delivery and Payment. Delivery of and payment for the Underwritten Securities and the Option Securities (if the option provided for in Section 2(b) hereof shall have

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been exercised on or before the third Business Day immediately preceding the Closing Date) shall be made on the date and at the time specified in Schedule I hereto or at such time on such later date not more than three Business Days after the foregoing date as the Representatives shall designate, which date and time may be postponed by agreement between the Representatives and the Company or as provided in Section 9 hereof (such date and time of delivery and payment for the Securities being herein called the “Closing Date”). Delivery of the Securities shall be made to the Representatives for the respective accounts of the several Underwriters against payment by the several Underwriters through the Representatives of the purchase price thereof to or upon the order of the Company by wire transfer payable in same-day funds to an account specified by the Company. Delivery of the Underwritten Securities and the Option Securities shall be made through the facilities of The Depository Trust Company unless the Representatives shall otherwise instruct.

If the option provided for in Section 2(b) hereof is exercised after the third Business Day immediately preceding the Closing Date, the Company will deliver the Option Securities (at the expense of the Company) to the Representatives, at 388 Greenwich Street, New York, New York, on the date specified by the Representatives (which shall be within three Business Days after exercise of said option) for the respective accounts of the Underwriters, against payment by the Underwriters through the Representatives of the purchase price thereof to or upon the order of the Company by wire transfer payable in same-day funds to an account specified by the Company. If settlement for the Option Securities occurs after the Closing Date, the Company will deliver to the Representatives on the settlement date for the Option Securities, and the obligation of the Underwriters to purchase the Option Securities shall be conditioned upon receipt of, supplemental opinions, certificates and letters confirming as of such date the opinions, certificates and letters delivered on the Closing Date pursuant to Section 6 hereof.

4. Offering by Underwriters. It is understood that the several Underwriters propose to offer the Securities for sale to the public as set forth in the Final Prospectus.

5. Agreements. The Company agrees with the several Underwriters that:

(a) Prior to the termination of the offering of the Securities, the Company will not file any amendment of the Registration Statement or supplement (including the Final Prospectus or any Preliminary Prospectus) to the Base Prospectus or any Rule 462(b) Registration Statement unless the Company has furnished you a copy for your review prior to filing and will not file any such proposed amendment or supplement to which you reasonably object. The Company will cause the Final Prospectus, properly completed, and any supplement thereto to be filed in a form approved by the Representatives with the Commission pursuant to the applicable paragraph of Rule 424(b) within the time period prescribed and will provide evidence satisfactory to the Representatives of such timely filing. The Company will promptly advise the Representatives (i) when the Final Prospectus, and any supplement thereto, shall have been filed (if required) with the Commission pursuant to Rule 424(b) or when any Rule 462(b) Registration Statement shall have been filed with the Commission, (ii) when, prior to termination of the offering of the Securities, any amendment to the Registration Statement shall have been filed or become effective, (iii) of any request by the Commission or its staff for any amendment of the Registration Statement, or any

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Rule 462(b) Registration Statement, or for any supplement to the Final Prospectus or for any additional information, (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or of any notice objecting to its use or the institution or threatening of any proceeding for that purpose and (v) of the receipt by the Company of any notification with respect to the suspension of the qualification of the Securities for sale in any jurisdiction or the institution or threatening of any proceeding for such purpose. The Company will use its best efforts to prevent the issuance of any such stop order or the occurrence of any such suspension or objection to the use of the Registration Statement and, upon such issuance, occurrence or notice of objection, to obtain as soon as possible the withdrawal of such stop order or relief from such occurrence or objection, including, if necessary, by filing an amendment to the Registration Statement or a new registration statement and using its best efforts to have such amendment or new registration statement declared effective as soon as practicable.

(b) If, at any time prior to the filing of the Final Prospectus pursuant to Rule 424(b), any event occurs as a result of which the Disclosure Package would include any untrue statement of a material fact or omit to state any material fact necessary to make the statements therein in the light of the circumstances under which they were made or the circumstances then prevailing not misleading, the Company will (i) notify promptly the Representatives so that any use of the Disclosure Package may cease until it is amended or supplemented; (ii) amend or supplement the Disclosure Package to correct such statement or omission; and (iii) supply any amendment or supplement to you in such quantities as you may reasonably request.

(c) If, at any time when a prospectus relating to the Securities is required to be delivered under the Act (including in circumstances where such requirement may be satisfied pursuant to Rule 172), any event occurs as a result of which the Final Prospectus as then supplemented would include any untrue statement of a material fact or omit to state any material fact necessary to make the statements therein in the light of the circumstances under which they were made at such time not misleading, or if it shall be necessary to amend the Registration Statement, file a new registration statement or supplement the Final Prospectus to comply with the Act or the Exchange Act or the respective rules thereunder, including in connection with use or delivery of the Final Prospectus, the Company promptly will (i) notify the Representatives of any such event, (ii) prepare and file with the Commission, subject to the second sentence of paragraph (a) of this Section 5, an amendment or supplement or new registration statement which will correct such statement or omission or effect such compliance, (iii) use its best efforts to have any amendment to the Registration Statement or new registration statement declared effective as soon as practicable in order to avoid any disruption in use of the Final Prospectus and (iv) supply any supplemented Final Prospectus to you in such quantities as you may reasonably request.

(d) As soon as practicable, the Company will make generally available to its security holders and to the Representatives an earnings statement or statements of the Company and its subsidiaries which will satisfy the provisions of Section 11(a) of the Act and Rule 158.

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(e) The Company will furnish to the Representatives and counsel for the Underwriters, without charge, signed copies of the Registration Statement (including exhibits thereto) and to the Underwriters a copy of the Registration Statement (without exhibits thereto) and, so long as delivery of a prospectus by the Underwriters or dealer may be required by the Act (including in circumstances where such requirement may be satisfied pursuant to Rule 172), as many copies of each Preliminary Prospectus, the Final Prospectus and each Issuer Free Writing Prospectus and any supplement thereto as the Representatives may reasonably request. The Company will pay the expenses of printing or other production of all documents relating to the offering.

(f) The Company will arrange, if necessary, for the qualification of the Securities for sale under the laws of such jurisdictions as the Representatives may designate and will maintain such qualifications in effect so long as required for the distribution of the Securities; provided that in no event shall the Company be obligated to qualify to do business in any jurisdiction where it is not now so qualified or to take any action that would subject it to service of process in suits, other than those arising out of the offering or sale of the Securities, in any jurisdiction where it is not now so subject.

(g) The Company agrees that, unless it has or shall have obtained the prior written consent of the Representatives, and each Underwriter, severally and not jointly, agrees with the Company that, unless it has or shall have obtained, as the case may be, the prior written consent of the Company, it has not made and will not make any offer relating to the Securities that would constitute an Issuer Free Writing Prospectus or that would otherwise constitute a “free writing prospectus” (as defined in Rule 405) required to be filed by the Company with the Commission or retained by the Company under Rule 433; provided that the prior written consent of the parties hereto shall be deemed to have been given in respect of the Free Writing Prospectuses included in Schedule III hereto. Any such free writing prospectus consented to by the Representatives or the Company is hereinafter referred to as a “Permitted Free Writing Prospectus.” The Company agrees that (x) it has treated and will treat, as the case may be, each Permitted Free Writing Prospectus as an Issuer Free Writing Prospectus and (y) it has complied and will comply, as the case may be, with the requirements of Rules 164 and 433 applicable to any Permitted Free Writing Prospectus, including in respect of timely filing with the Commission, legending and record keeping.

(h) The Company will not sell, offer or agree to sell, contract to sell, hypothecate, pledge, grant any option to sell or otherwise dispose of, directly or indirectly, any shares of Common Stock or securities convertible into or exercisable or exchangeable for Common Stock or warrants or other rights to purchase Common Stock or enter into any swap or any other agreement or any transaction that transfers, in whole or in part, directly or indirectly, the economic consequences of ownership of Common Stock, or file or cause to be declared effective a registration statement under the Securities Act relating to the offer and sale of any shares of Common Stock or securities convertible into or exercisable or exchangeable for Common Stock or other rights to purchase Common Stock for a period of 30 days after the date hereof (the “Lock-Up Period”), without the prior written consent of the Representative, except for (i) the sales to the Underwriters pursuant to this Agreement and (ii) (x) the issuance of employee

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stock options granted under the Company’s employee benefit plans, (y) securities issued in connection with the Company’s dividend reinvestment plan, as described in the Registration Statement and the Prospectus or incorporated by reference therein or (z) securities issued in connection with strategic acquisitions by the Company or transactions involving the exchange of the Company’s stock for the stock of other entities;

(i) The Company will not take, directly or indirectly, any action designed to or that would constitute or that might reasonably be expected to cause or result in, under the Exchange Act or otherwise, stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

(j) The Company agrees to pay the costs and expenses relating to the following matters: (i) the preparation, printing or reproduction and filing with the Commission of the Registration Statement (including financial statements and exhibits thereto), each Preliminary Prospectus, the Final Prospectus and each Issuer Free Writing Prospectus, and each amendment or supplement to any of them; (ii) the printing (or reproduction) and delivery (including postage, air freight charges and charges for counting and packaging) of such copies of the Registration Statement, each Preliminary Prospectus, the Final Prospectus and each Issuer Free Writing Prospectus, and all amendments or supplements to any of them, as may, in each case, be reasonably requested for use in connection with the offering and sale of the Securities; (iii) the preparation, printing, authentication, issuance and delivery of certificates for the Securities, including any stamp or transfer taxes in connection with the original issuance and sale of the Securities; (iv) the printing (or reproduction) and delivery of this Agreement, any blue sky memorandum and all other agreements or documents printed (or reproduced) and delivered in connection with the offering of the Securities; (v) the registration of the Securities under the Exchange Act and the listing of the Securities on the New York Stock Exchange; (vi) any registration or qualification of the Securities for offer and sale under the securities or blue sky laws of the several states (including filing fees and the reasonable fees and expenses of counsel for the Underwriters relating to such registration and qualification); (vii) any filings required to be made with the NASD, Inc. (including filing fees and the reasonable fees and expenses of counsel for the Underwriters relating to such filings); (viii) the transportation and other expenses incurred by or on behalf of Company representatives in connection with presentations to prospective purchasers of the Securities; (ix) the fees and expenses of the Company’s accountants and the fees and expenses of counsel (including local and special counsel) for the Company; and (x) all other costs and expenses incident to the performance by the Company of its obligations hereunder.

6. Conditions to the Obligations of the Underwriters. The obligations of the Underwriters to purchase the Underwritten Securities and the Option Securities, as the case may be, shall be subject to the accuracy of the representations and warranties on the part of the Company contained herein as of the Execution Time, the Closing Date and any settlement date pursuant to Section 3 hereof, to the accuracy of the statements of the Company made in any certificates pursuant to the provisions hereof, to the performance by the Company of its obligations hereunder and to the following additional conditions:

(a) The Final Prospectus, and any supplement thereto, have been filed in the manner and within the time period required by Rule 424(b); any material required to be filed by the Company pursuant to Rule 433(d) under the Act, shall have been filed with the Commission within the applicable time periods prescribed for such filings by Rule 433; and no stop order suspending the effectiveness of the Registration Statement or any notice objecting to its use shall have been issued and no proceedings for that purpose shall have been instituted or threatened.

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(b) The Company shall furnish to the Underwriters at the Closing Date and at each settlement date, if any, opinions of Thacher Proffitt & Wood LLP, special counsel to the Company and its subsidiaries, and Ballard, Spahr, Andrews & Ingersoll, LLP, Maryland corporate counsel to the Company and its subsidiaries, as to matters of Maryland law, and Alan B. Horn, general counsel of the Company, addressed to the Underwriters and dated the Closing Date and any settlement date and in form and substance satisfactory to Underwriters’ counsel, in the form set forth in Exhibit A hereto:

(c) The Representatives shall have received from Deloitte & Touche LLP, letters dated, respectively, as of the date of this Agreement, the Closing Date and any settlement date, as the case may be, addressed to the Representatives, in form and substance satisfactory to the Representatives, relating to the financial statements of the Company and its subsidiaries, including any pro forma financial statements and such other matters customarily covered by comfort letters issued in connection with registered public offerings in the forms heretofore approved by the Representatives.

(d) The Representatives shall have received at the Closing Date and at each settlement date, as applicable, the favorable opinion of Cadwalader, Wickersham & Taft LLP, counsel for the Underwriters, dated the Closing Date or any settlement date, as applicable, addressed to the Representatives with respect to such matters as the Representatives reasonably may request.

(e) No amendment or supplement to the Registration Statement or Prospectus shall have been filed to which the Underwriters shall have objected in writing.

(f) Subsequent to the Execution Time or, if earlier, the dates as of which information is given in the Registration Statement (exclusive of any amendment thereof) and the Final Prospectus (exclusive of any amendment or supplement thereto), there shall not have been any change, or any development involving a prospective change, in or affecting the condition (financial or otherwise), earnings, business or properties of the Company and its subsidiaries taken as a whole, whether or not arising from transactions in the ordinary course of business, except as set forth in or contemplated in the Disclosure Package and the Final Prospectus (exclusive of any amendment or supplement thereto) the effect of which, is, in the sole judgment of the Representatives, so material and adverse as to make it impractical or inadvisable to proceed with the offering or delivery of the Securities as contemplated by the Registration Statement (exclusive of any amendment thereof), the Disclosure Package and the Final Prospectus (exclusive of any amendment or supplement thereto).

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(g) Between the time of execution of this Agreement and the Closing Date or any settlement date, as the case may be, (i) no material and unfavorable change or any development involving a prospective material adverse change, financial or otherwise (other than such change or development specifically identified in the Registration Statement and Base Prospectus at the time of this Agreement), in the business, properties, financial condition, results of operation of the Company and its subsidiaries taken as a whole shall occur or become known (ii) no obligation, direct or contingent, which is material to the Company and its subsidiaries taken as a whole, shall have been incurred by the Company or its subsidiaries, other than in the ordinary course of business, (iii) there shall be no material change in the capital stock or outstanding indebtedness of the Company or its subsidiaries, other than in the ordinary course of business and (iv) there shall not have been any dividend or distribution of any kind declared, paid or made on the capital stock of the Company (except as described in the Base Prospectus as amended and supplemented).

(h) The NASD shall not have raised any objection with respect to the fairness and reasonableness of the underwriting terms and arrangements.

(i) The Securities shall have been approved for listing on the New York Stock Exchange.

(j) The Company will, at the Closing Date and at any settlement date, deliver to the Underwriters a certificate of its Chairman of the Board and Chief Executive Officer and its Executive Vice President and Chief Financial Officer to the effect that, to each of such officer’s knowledge, the representations and warranties of the Company set forth in this Agreement are true and correct on and as of such date with the same effect as if made on such date, and the Company has performed all covenants and agreements and satisfied all conditions contained in this Agreement required to be performed or satisfied by it at or prior to such date and the conditions set forth in paragraphs (f), (g) and (i) have been satisfied, in each case as of such date.

(k) The Company shall have furnished to the Underwriters such other documents and certificates as to the accuracy and completeness of any statement in the Registration Statement, Disclosure Package and the Final Prospectus, the representations, warranties and statements of the Company contained herein, and the performance by the Company of its covenants contained herein, and the fulfillment of any conditions contained herein, as of the Closing Date or any settlement date as the Underwriters may reasonably request.

(l) The Company shall have performed such of its obligations under this Agreement as are to be performed by the terms hereof at or before the Closing Date or any settlement date.

7. Reimbursement of Underwriters’ Expenses. If the sale of the Securities provided for herein is not consummated because any condition to the obligations of the Underwriters set forth in Section 6 hereof is not satisfied, because of any termination pursuant to Section 10 hereof or because of any refusal, inability or failure on the part of the Company to

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perform any agreement herein or comply with any provision hereof other than by reason of a default by the Underwriters, the Company will reimburse the Underwriters severally through Citigroup Global Markets Inc. on demand for all expenses (including reasonable fees and disbursements of counsel) that shall have been incurred by them in connection with the proposed purchase and sale of the Securities.

8. Indemnification and Contribution. (a) The Company agrees to indemnify and hold harmless each Underwriter, the directors, officers, employees and agents of each Underwriter and each person who controls any Underwriter within the meaning of either the Act or the Exchange Act against any and all losses, claims, damages or liabilities, joint or several, to which they or any of them may become subject under the Act, the Exchange Act or other Federal or state statutory law or regulation, at common law or otherwise, insofar as such losses, claims, damages or liabilities (or actions in respect thereof) arise out of or are based upon any untrue statement or alleged untrue statement of a material fact contained in the registration statement for the registration of the Securities as originally filed or in any amendment thereof, or in the Base Prospectus, any Preliminary Prospectus or any other preliminary prospectus supplement relating to the Securities, Disclosure Package and the Final Prospectus or any Issuer Free Writing Prospectus, or in any amendment thereof or supplement thereto, or arise out of or are based upon the omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading, and agrees to reimburse each such indemnified party, as incurred, for any legal or other expenses reasonably incurred by them in connection with investigating or defending any such loss, claim, damage, liability or action; provided, however, that the Company will not be liable in any such case to the extent that any such loss, claim, damage or liability arises out of or is based upon any such untrue statement or alleged untrue statement or omission or alleged omission made therein in reliance upon and in conformity with written information furnished to the Company by or on behalf of the Underwriters through the Representatives specifically for inclusion therein. This indemnity agreement will be in addition to any liability which the Company may otherwise have.

(b) The Underwriters severally and not jointly agrees to indemnify and hold harmless the Company, each of its directors, each of its officers who signs the Registration Statement, and each person who controls the Company within the meaning of either the Act or the Exchange Act, to the same extent as the foregoing indemnity from the Company to the Underwriters, but only with reference to written information relating to the Underwriters furnished to the Company by or on behalf of the Underwriters through the Representatives specifically for inclusion in the documents referred to in the foregoing indemnity. This indemnity agreement will be in addition to any liability which the Underwriters may otherwise have. The Company acknowledges that the statements set forth (i) in the last paragraph of the cover page regarding delivery of the Securities and, under the heading “Underwriting” or “Plan of Distribution”, (ii) the list of Underwriters and their respective participation in the sale of the Securities, (iii) the sentences related to concessions and reallowances and (iv) the paragraph related to stabilization, syndicate covering transactions and penalty bids in any Preliminary Prospectus and the Final Prospectus constitute the only information furnished in writing by or on behalf of the Underwriters for inclusion in any Preliminary Prospectus, the Final Prospectus or any Issuer Free Writing Prospectus.

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(c) Promptly after receipt by an indemnified party under this Section 8 of notice of the commencement of any action, such indemnified party will, if a claim in respect thereof is to be made against the indemnifying party under this Section 8, notify the indemnifying party in writing of the commencement thereof; but the failure so to notify the indemnifying party (i) will not relieve it from liability under paragraph (a) or (b) above unless and to the extent it did not otherwise learn of such action and such failure results in the forfeiture by the indemnifying party of substantial rights and defenses and (ii) will not, in any event, relieve the indemnifying party from any obligations to any indemnified party other than the indemnification obligation provided in paragraph (a) or (b) above. The indemnifying party shall be entitled to appoint counsel of the indemnifying party’s choice at the indemnifying party’s expense to represent the indemnified party in any action for which indemnification is sought (in which case the indemnifying party shall not thereafter be responsible for the fees and expenses of any separate counsel retained by the indemnified party or parties except as set forth below); provided, however, that such counsel shall be satisfactory to the indemnified party. Notwithstanding the indemnifying party’s election to appoint counsel to represent the indemnified party in an action, the indemnified party shall have the right to employ separate counsel (including local counsel), and the indemnifying party shall bear the reasonable fees, costs and expenses of such separate counsel if (i) the use of counsel chosen by the indemnifying party to represent the indemnified party would present such counsel with a conflict of interest, (ii) the actual or potential defendants in, or targets of, any such action include both the indemnified party and the indemnifying party and the indemnified party shall have reasonably concluded that there may be legal defenses available to it and/or other indemnified parties which are different from or additional to those available to the indemnifying party, (iii) the indemnifying party shall not have employed counsel satisfactory to the indemnified party to represent the indemnified party within a reasonable time after notice of the institution of such action or (iv) the indemnifying party shall authorize the indemnified party to employ separate counsel at the expense of the indemnifying party. An indemnifying party will not, without the prior written consent of the indemnified parties, settle or compromise or consent to the entry of any judgment with respect to any pending or threatened claim, action, suit or proceeding in respect of which indemnification or contribution may be sought hereunder (whether or not the indemnified parties are actual or potential parties to such claim or action) unless such settlement, compromise or consent includes an unconditional release of each indemnified party from all liability arising out of such claim, action, suit or proceeding.

(d) In the event that the indemnity provided in paragraph (a), (b) or (c) of this Section 8 is unavailable to or insufficient to hold harmless an indemnified party for any reason, the Company and the Underwriters severally agree to contribute to the aggregate losses, claims, damages and liabilities (including legal or other expenses reasonably incurred in connection with investigating or defending the same) (collectively “Losses”) to which the Company and one or more of the Underwriters may be subject in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and by the Underwriters on the other from the offering of the Securities;

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provided, however, that in no case shall any Underwriter (except as may be provided in any agreement among underwriters relating to the offering of the Securities) be responsible for any amount in excess of the underwriting discount or commission applicable to the Securities purchased by such Underwriter hereunder. If the allocation provided by the immediately preceding sentence is unavailable for any reason, the Company and the Underwriters severally shall contribute in such proportion as is appropriate to reflect not only such relative benefits but also the relative fault of the Company on the one hand and of the Underwriters on the other in connection with the statements or omissions which resulted in such Losses as well as any other relevant equitable considerations. Benefits received by the Company shall be deemed to be equal to the total net proceeds from the offering (before deducting expenses) received by it, and benefits received by the Underwriters shall be deemed to be equal to the total underwriting discounts and commissions, in each case as set forth on the cover page of the Final Prospectus. Relative fault shall be determined by reference to, among other things, whether any untrue or any alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information provided by the Company on the one hand or the Underwriters on the other, the intent of the parties and their relative knowledge, access to information and opportunity to correct or prevent such untrue statement or omission. The Company and the Underwriters agree that it would not be just and equitable if contribution were determined by pro rata allocation or any other method of allocation which does not take account of the equitable considerations referred to above. Notwithstanding the provisions of this paragraph (d), no person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation. For purposes of this Section 8, each person who controls an Underwriter within the meaning of either the Act or the Exchange Act and each director, officer, employee and agent of an Underwriter shall have the same rights to contribution as such Underwriter, and each person who controls the Company within the meaning of either the Act or the Exchange Act, each officer of the Company who shall have signed the Registration Statement and each director of the Company shall have the same rights to contribution as the Company, subject in each case to the applicable terms and conditions of this paragraph (d).

9. Reserved.

10. Termination. This Agreement shall be subject to termination in the absolute discretion of the Representatives, by notice given to the Company prior to delivery of and payment for the Securities, if at any time prior to such delivery and payment (i) trading in the Company’s Common Stock shall have been suspended by the Commission or the New York Stock Exchange or trading in securities generally on the New York Stock Exchange shall have been suspended or limited or minimum prices shall have been established on such exchange, (ii) a banking moratorium shall have been declared either by Federal or New York State authorities or (iii) there shall have occurred any outbreak or escalation of hostilities, declaration by the United States of a national emergency or war, or other calamity or crisis the effect of which on financial markets is such as to make it, in the sole judgment of the Representatives, impractical or inadvisable to proceed with the offering or delivery of the Securities as contemplated by any Preliminary Prospectus, the Disclosure Package or the Final Prospectus (exclusive of any amendment or supplement thereto).

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11. Representations and Indemnities to Survive. The respective agreements, representations, warranties, indemnities and other statements of the Company or its officers and of the Underwriters set forth in or made pursuant to this Agreement will remain in full force and effect, regardless of any investigation made by or on behalf of any Underwriter or the Company or any of the officers, directors, employees, agents or controlling persons referred to in Section 8 hereof, and will survive delivery of and payment for the Securities. The provisions of Sections 7 and 8 hereof shall survive the termination or cancellation of this Agreement.

12. Notices. All communications hereunder will be in writing and effective only on receipt, and, if sent to the Representatives, will be mailed, delivered or telefaxed to the Citigroup Global Markets Inc. General Counsel (fax no.: (212) 816- 7912) and confirmed to the General Counsel, Citigroup Global Markets Inc., at 388 Greenwich Street, New York, New York, 10013, Attention: General Counsel; or, if sent to the Company, will be mailed, delivered or telefaxed to ###-###-#### and confirmed to it at 538 Broadhollow Road, Melville, New York 11747, Attention: Alan Horn.

13. Successors. This Agreement will inure to the benefit of and be binding upon the parties hereto and their respective successors and the officers, directors, employees, agents and controlling persons referred to in Section 8 hereof, and no other person will have any right or obligation hereunder.

14. No fiduciary duty. The Company hereby acknowledges that (a) the purchase and sale of the Securities pursuant to this Agreement is an arm’s-length commercial transaction between the Company, on the one hand, and the Underwriters and any affiliate through which it may be acting, on the other, (b) the Underwriters are acting as principal and not as an agent or fiduciary of the Company and (c) the Company’s engagement of the Underwriters in connection with the offering and the process leading up to the offering is as independent contractors and not in any other capacity. Furthermore, the Company agrees that it is solely responsible for making its own judgments in connection with the offering (irrespective of whether any of the Underwriters has advised or is currently advising the Company on related or other matters). The Company agrees that it will not claim that the Underwriters have rendered advisory services of any nature or respect, or owe an agency, fiduciary or similar duty to the Company, in connection with such transaction or the process leading thereto.

15. Integration. This Agreement supersedes all prior agreements and understandings (whether written or oral) between the Company and the Underwriters, or any of them, with respect to the subject matter hereof.

16. Applicable Law. This Agreement will be governed by and construed in accordance with the laws of the State of New York applicable to contracts made and to be performed within the State of New York.

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17. Waiver of Jury Trial. The Company hereby irrevocably waives, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to this Agreement or the transactions contemplated hereby.

18. Counterparts. This Agreement may be signed in one or more counterparts, each of which shall constitute an original and all of which together shall constitute one and the same agreement.

19. Headings. The section headings used herein are for convenience only and shall not affect the construction hereof.

20. Definitions. The terms that follow, when used in this Agreement, shall have the meanings indicated.

“Act” shall mean the Securities Act of 1933, as amended, and the rules and regulations of the Commission promulgated thereunder.

“Base Prospectus” shall mean the base prospectus referred to in paragraph 1(a) above contained in the Registration Statement at the Execution Time.

“Business Day” shall mean any day other than a Saturday, a Sunday or a legal holiday or a day on which banking institutions or trust companies are authorized or obligated by law to close in New York City.

“Commission” shall mean the Securities and Exchange Commission.

“Disclosure Package” shall mean (i) the Base Prospectus, (ii) the Preliminary Prospectus, if any, used most recently prior to the Execution Time, (iii) the Schedule IV information, (iv) the Issuer Free Writing Prospectuses, if any, identified in Schedule III hereto, and (v) any other Free Writing Prospectus that the parties hereto shall hereafter expressly agree in writing to treat as part of the Disclosure Package.

“Effective Date” shall mean each date and time that the Registration Statement, any post-effective amendment or amendments thereto and any Rule 462(b) Registration Statement became or becomes effective.

“Exchange Act” shall mean the Securities Exchange Act of 1934, as amended, and the rules and regulations of the Commission promulgated thereunder.

“Execution Time” shall mean the date and time that this Agreement is executed and delivered by the parties hereto.

“Final Prospectus” shall mean the prospectus supplement relating to the Securities that was first filed pursuant to Rule 424(b) after the Execution Time, together with the Base Prospectus.

“Free Writing Prospectus” shall mean a free writing prospectus, as defined in Rule 405.

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“Issuer Free Writing Prospectus” shall mean an issuer free writing prospectus, as defined in Rule 433.

“Preliminary Prospectus” shall mean any preliminary prospectus supplement to the Base Prospectus referred to in paragraph 1(a) above which is used prior to the filing of the Final Prospectus, together with the Base Prospectus.

“Registration Statement” shall mean the registration statement referred to in paragraph 1(a) above, under File No. 333-121304, including exhibits and financial statements and any prospectus supplement relating to the Securities that is filed with the Commission pursuant to Rule 424(b) and deemed part of such registration statement pursuant to Rule 430B, as amended on each Effective Date and, in the event any post-effective amendment thereto or any Rule 462(b) Registration Statement becomes effective prior to the Closing Date, shall also mean such registration statement as so amended or such Rule 462(b) Registration Statement, as the case may be.

“Rule 158”, “Rule 163”, “Rule 164”, “Rule 172”, “Rule 405”, “Rule 415”, “Rule 424”, “Rule 430B”, “Rule 433” and “Rule 462” refer to such rules under the Act.

“Rule 462(b) Registration Statement” shall mean a registration statement and any amendments thereto filed pursuant to Rule 462(b) relating to the offering covered by the registration statement referred to in Section 1(a) hereof.

“Schedule IV information” shall mean the information set forth on Schedule IV to this Underwriting Agreement.

“Well-Known Seasoned Issuer” shall mean a well-known seasoned issuer, as defined in Rule 405.

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If the foregoing is in accordance with your understanding of our agreement, please sign and return to us the enclosed duplicate hereof, whereupon this letter and your acceptance shall represent a binding agreement among the Company and the Underwriters.

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SCHEDULE I

Underwriting Agreement dated April 30, 2007

Registration Statement No. 333-121304

Representatives: Citigroup Global Markets Inc.

Title and Description of Securities:

Title: Common Stock

Number of Underwritten Securities to be sold by the Company: 4,000,000

Number of Option Securities to be sold by the Company: 600,000

Price per Share to the Underwriters: $23.10

Closing Date, Time and Location:

May 4, 2007, at 10:00 a.m. at:

Cadwalader, Wickersham & Taft LLP

One World Financial Center

New York, NY 10281

Type of Offering: Non-Delayed

Date referred to in Section 5(h) after which the Company may offer or sell securities issued by the Company without the consent of the Representatives:

SCHEDULE II

SCHEDULE III

Schedule of Free Writing Prospectuses included in the Disclosure Package:

None.

SCHEDULE IV

Price to Public- Variable Price

Number of Underwritten Securities to be sold by the Company: 4,000,000

Number of Option Securities to be sold by the Company: 600,000

Underwriter: Citigroup Global Markets Inc.