The president shall sign all contracts on behalf of the district and shall certify to the county auditor all lawful demands against the district payable from the memorial district fund and from the memorial district bond fund after such demands have first been approved by at least three members of the board. The president shall also perform any other duties imposed by the board. The secretary shall countersign all contracts on behalf of the district and perform any other duties precribed by the board. A majority of the board shall constitute a quorum for the transaction of business, but all official acts of the board must receive the affirmative vote, signature, or approval, as the case may require, of at least three members of the board.