Nothing in this chapter shall be construed to constitute authorization hereunder for—
(a)the use of the cost-plus-a-percentage-of-cost system of contracting;
(b)any contract in violation of existing law relating to limitation of profits;
(c)the negotiation of purchases of or contracts for property or services required by law to be procured by formal advertising and competitive bidding;
(d)the waiver of any bid, payment, performance, or other bond required by law;
(e)the amendment of a contract negotiated under section
2304(a)(15)[1] of title
10 or under section
252(c)(13)[1] of title
41, to increase the contract price to an amount higher than the lowest rejected bid of any responsible bidder; or
(f)the formalization of an informal commitment, unless it is found that at the time the commitment was made it was impracticable to use normal procurement procedures.