PUBLIC LAWS-CH. 251 -MAY 13, 1946 Auditing. Determination of times and amounts. 54 Stat. 1179. 50U.S.C.app. 511 (1);Supp. V, app §511 note. project cost as he determines to be reasonable and no project costs in excess of the definite amount stated in the grant agreement shall be allowable. The Administrator is authorized to prescribe such regulations, includ- ing regulations with respect to the auditing of project costs, as he may deem necessary to effectuate the purposes of this section. PAYMENTS SEc. 14 . The Administrator, after consultation with the sponsor or sponsors with which a grant agreement has been entered into, shall determine at what times, and in what amounts, payments shall be made under this Act. The aggregate of such payments at any time with respect to a particular project shall not exceed a percentage of the project costs of the airport development which has been performed up to that time (and which the sponsor or sponsors to which the pay- ments are to be made certify to have been performed in accordance with the approved plans and specifications for such project), equal to the percentage of the allowable project costs of the project deter- mined to be the United States share of such costs; and if the Adminis- trator shall determine at any time that the aggregate of such payments exceeds the United States share of the allowable project costs of such project the United States shall be entitled to recover such excess. Such payments shall be made to such official or officials or depository, author- ized by law to receive public funds, as may be designated by the sponsor or sponsors entitled to such payments. PERFORMANCE OF CONSTRUCTIONI WORK Regulations of the Administrator SEC. 15. (a) The construction work on any approved project shall be subject to inspection and approval by the Administrator and in accordance with regulations prescribed by him. Such regulations shall require such cost and progress reporting by the sponsor or spon- sors of such project as the Administrator shall deem necessary. No such regulation shall have the effect of altering any contract in connec- tion with any project entered into without actual notice of the regu- lation. Minimum Rates of Wages (b) All contracts for work on projects approved under this Act which involves labor shall contain provisions establishing minimum rates of wages, to be predetermined by the Secretary of Labor, which contractors shall pay to skilled and unskilled labor, and such minimum rates shall be stated in the invitation for bids and shall be included in proposals or bids for the work. Other Provisions as to Labor (c) All contracts for work on projects approved under this Act which involves labor shall contain such provisions as are necessary to insure (1) that no convict labor shall be employed; and (2) that in the employment of labor (except in executive, administrative, and supervisory positions), preference shall be given, where they are quali- fied, to individuals who have served as persons in the military service of the United States (as defined in section 101 (1) of the Soldiers' and Sailors' Civil Relief Act of 1940), and who have been honorably dis- charged from such service: Provided,That such preference shall apply only where such labor is available and qualified to perform the work to which the employment relates. [60 STAT.