(a) If revenue bonds issued under this chapter state that they are secured in whole or in part by a pledge of the proceeds from a contract between the municipality and another person, a copy of the contract and of the proceedings authorizing the contract must be submitted to the attorney general with the bond record.
(b) The approval by the attorney general of the bonds is approval of the contract.
(c) After approval, the contract is incontestable except for forgery or fraud.