For the purpose of conducting such audit the Comptroller General is authorized in his discretion to employ by contract, without regard to section
5 of title
41, professional services of firms and organizations of certified public accountants, with the concurrence of the Corporation, for temporary periods or for special purposes. The Corporation shall reimburse the Government Accountability Office for the cost of any such audit as billed therefor by the Comptroller General, and the Government Accountability Office shall deposit the sums so reimbursed into the Treasury as miscellaneous receipts.