the use of the cost-plus-a-percentage-of-cost system of contracting;

any contract in violation of existing law relating to limitation of profits;

the negotiation of purchases of or contracts for property or services required by law to be procured by formal advertising and competitive bidding;

the waiver of any bid, payment, performance, or other bond required by law;

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

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.