Exhibit 10.25 Rabobank New York Branch 245 Park Avenue New York, NY 10167-0062 U.S.A. 212-916-7800 April 26, 1999 Ambac Assurance Corporation One State Street Plaza New York, New York 10004 Attn: Anne Gill Deutsche Bank AG, New York Branch, as Agent 31 West 52nd Street New York, New York 10019 Acceptance Notice - ----------------- Ladies and Gentlemen: Reference is hereby made to the Amended and Restated Credit Agreement dated as of December 2, 1998 (the "Credit Agreement"), among Ambac Assurance Corporation (the "Borrower"), the Banks party thereto from time to time and Deutsche Bank AG, New York Branch, as Agent (the "Agent"), and (b) the Increase Request dated April 23, 1999 delivered by the Borrower. Terms defined in the Credit Agreement are used herein as therein defined unless otherwise defined herein. The undersigned Bank is a Triple-A Bank (as defined in the Increase Request referred to above) and is willing to increase the amount of its Commitment by $20,000,000. In the event that our offer in the next preceding sentence is accepted by the Borrower by executing the acceptance below and returning an accepted copy to the undersigned Bank (with a copy to the Agent) on or prior to May 3, 1999, then our Commitment shall, effective as of May 3, 1999, be increased by the amount set forth in the next preceding paragraph and we agree that we will perform in accordance with their terms all of the obligations which by the terms of the Credit Agreement are required to be performed by it as a Bank with such an increased Commitment. If our Commitment is so increased, we understand that, upon the surrender by us to the Borrower of the Note previously issued to us, a new Note will be issued to us in the stated amount of our increased Commitment. Very truly yours, COOPERATIVE CENTRALE RAIFFEISEN-BOERENLEENBANK B.A., "RABOBANK NEDERLAND", NEW YORK BRANCH By: /s/ Angela R. Reilly ----------------------------------- Name: Angela R. Reilly Title: Vice President By: /s/ Michel de Konkoly Thege ----------------------------------- Name: Michel de Konkoly Thege Title: Managing Director ACCEPTED: AMBAC ASSURANCE CORPORATION By: /s/ Robert W. Starr -------------------------------- Name: Robert W. Starr Title: First Vice President ACKNOWLEDGED: DEUTSCHE BANK AG, New York Branch, as Agent By: /s/ Ira Lubinsky -------------------------------- Name: Ira Lubinsky Title: Vice President