EXHIBIT 4 [LOGO]3G Capital Partners Ltd. • December 19th, 2007 • Railroads, line-haul operating
The purpose of this letter agreement is to confirm the agreement between The Children's Investment Fund Management (UK) LISP ("TCI Management") and 3G Capital Partners Ltd. ("3G Capital Partners" and, together with TCI Management, the "Parties") to coordinate certain of their efforts with respect to: (i) the purchase and sale of common stock of the Company and/or options, swaps or other derivative securities or instruments that constitute or may by their terms create beneficial ownership of the common stock of the Company ("Securities"); and (ii) the proposal of certain actions and/or transactions to the Company. This letter agreement extends to any and all investment funds, managed accounts and other investment vehicles managed or advised by TCI Management and 3G Capital Partners (individually a "Subject Fund", collectively the "Subject Funds"). Schedule I attached hereto sets forth all of the Securities held by the Subject Funds.
