Tony is the managing director of Aeroventure Ltd, a flight school that trains pilots and offers leisure flights to tourists. The board of directors passes a resolution limiting Tony's authority. He is not allowed to enter into any contract exceeding $25,000 of spending without written approval from the board. Tony is given the opportunity to purchase a bargain light aircraft for $35,000, which will be ideal for training young people, so he signs an agreement with the seller on behalf of Aeroventure without consulting the board.

How much is the board bound to pay, if any, under the law of agency?