(a) As used in this Code section, the term "building and construction materials" means all building and construction materials, supplies, fixtures, or equipment, any combination of such items, and any other leased or purchased articles when the materials, supplies, fixtures, equipment, or articles are to be utilized or consumed during construction or are to be incorporated into construction work pursuant to a bona fide written construction contract.

(b) No tax provided for in this article shall be imposed upon the sale or use of building and construction materials when the contract pursuant to which the materials are purchased or used was advertised for bid prior to the voters' approval of the levy of the tax and the contract was entered into as a result of a bid actually submitted in response to the advertisement prior to approval of the levy of the tax.