Exhibit 4(b)

Exhibit 4(b)

AMENDING AGREEMENT

THIS AGREEMENT is made as of September 23, 2003

BETWEEN:

      WHEREAS the parties hereto have agreed to amend and supplement certain provisions of the Credit Agreement as hereinafter set forth;

      NOW THEREFORE THIS AGREEMENT WITNESSES that in consideration of the covenants and agreements herein contained and other good and valuable consideration, the receipt and sufficiency of which are hereby conclusively acknowledged by each of the parties hereto, the parties hereto covenant and agree as follows:

1.   Interpretation

1.1. In this Agreement and the recitals hereto, unless something in the subject matter or context is inconsistent therewith:

“Agreement” means this agreement, as amended, modified, supplemented or restated from time to time.

“Credit Agreement” means the term credit agreement made as of September 25, 2001 between Borrower, the Lenders listed in Schedule A thereto and such other financial institutions as become party thereto as lenders, and the Agent.

1.2. Capitalized terms used herein without express definition shall have the same meanings herein as are ascribed thereto in the Credit Agreement.

1.3. The division of this Agreement into Sections and the insertion of headings are for convenience of reference only and shall not affect the construction or interpretation of this Agreement. The terms “this Agreement”, “hereof”, “hereunder” and similar expressions refer to this Agreement and not to any particular Section or other portion hereof and include any agreements supplemental hereto.

1.4. This Agreement shall be governed by and construed in accordance with the laws of the Province of Ontario and the federal laws of Canada applicable therein.

2.   Amendments and Supplements

2.1. Amendments to Applicable Margin. Section 1.01 of the Credit Agreement is hereby amended by deleting the existing definition of “Applicable Margin” in its entirety and substituting the following therefor:

2.2. Amendments to Standby Fee Rate. Section 1.01 of the Credit Agreement is hereby amended by deleting the existing definition of “Standby Fee Rate” in its entirety and substituting the following therefor:

2.3. Increase of Credit Facility. Section 2.01 of the Credit Agreement is hereby amended to delete the amount “U.S.$650,000,000” on third line thereof and to substitute therefor “U.S.$750,000,000”; for certainty, the parties hereto confirm and agree that the amount of the Credit Facility shall be and is hereby increased from U.S.$650,000,000 to U.S.$750,000,000.

2.4. Addition of New Lenders.

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2.5. New Schedule A; Revised Commitments. Schedule A to the Credit Agreement is hereby deleted in its entirety and replaced with Schedule A attached hereto, inter alia, to reflect changes in the Individual Commitments of Lenders and the addition of the New Lenders.

2.6. Extension of Conversion Date. The Conversion Date is hereby extended to September 21, 2004 pursuant to Section 1.13 of the Credit Agreement with respect to each Lender.

2.7. Addition of Affirmative Covenant. Section 11.01 of the Credit Agreement is hereby amended to add the following new covenant as Section 11.01(n):

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3.   Representations and Warranties

      The Borrower hereby represents and warrants as follows to each Lender and the Agent and acknowledges and confirms that each Lender and the Agent is relying upon such representations and warranties:

      The representations and warranties set out in this Agreement shall survive the execution and delivery of this Agreement and the making of each Accommodation, notwithstanding any investigations or examinations which may be made by or on behalf of the Agent, the Lenders or Lenders’ counsel. Such representations and warranties shall survive until the Credit Agreement has been terminated.

4.   Conditions Precedent

      The amendments and supplements to the Credit Agreement contained herein shall be effective upon, and shall be subject to, the satisfaction of the following conditions precedent:

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The foregoing conditions precedent are inserted for the sole benefit of the Lenders and the Agent and may be waived in writing by the Lenders, in whole or in part (with or without terms and conditions).

5.   Confirmation of Credit Agreement and other Loan Documents

      The Credit Agreement and the other Loan Documents to which the Borrower is a party and all covenants, terms and provisions thereof, except as expressly amended and supplemented by this Agreement, shall be and continue to be in full force and effect and the Credit Agreement as amended and supplemented by this Agreement and each of the other Loan Documents to which the Borrower is a party is hereby ratified and confirmed and shall from and after the date hereof continue in full force and effect as herein amended and supplemented, with such amendments and supplements being effective from and as of the date hereof upon satisfaction of the conditions precedent set forth in Section 4 hereof.

6.   Further Assurances

      The parties hereto shall from time to time do all such further acts and things and execute and deliver all such documents as are required in order to effect the full intent of and fully perform and carry out the terms of this Agreement.

7.   Enurement

      This Agreement shall enure to the benefit of and shall be binding upon the parties hereto and their respective successors and permitted assigns.

8.   Counterparts

      This Agreement may be executed in any number of counterparts, each of which shall be deemed to be an original and all of which taken together shall be deemed to constitute one and the same instrument, and it shall not be necessary in making proof of this Agreement to produce or account for more than one such counterpart. Such executed counterparts may be delivered by facsimile transmission and, when so delivered, shall constitute a binding agreement of the parties hereto.

      IN WITNESS WHEREOF the parties hereto have executed this Agreement.

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Schedule A

Individual Commitments

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