The contract and bid specification shall contain a provision specifying the minimum wage to be paid to each class of service employee engaged in the performance of the contract or any subcontract, as determined by the Secretary or the Secretary’s authorized representative, in accordance with prevailing rates in the locality, or, where a collective-bargaining agreement covers the service employees, in accordance with the rates provided for in the agreement, including prospective wage increases provided for in the agreement as a result of arm’s length negotiations. In any case the minimum wage may not be less than the minimum wage specified in
section 6704 of this title.