No cost-reimbursement contract may be made unless the Purchasing Agent determines or approves a using agency's determination that such contract is likely to be more beneficial to the County than any other type of contract. Each contractor under a cost-reimbursement type contract shall obtain approval of the County, as provided for in the contract, before entering into: A cost-reimbursement type subcontract; or Any other type of subcontract involving more than $25,000.00, or 5% of the estimated cost of the prime contract, whichever amount is less. Except with respect to firm fixed-price type contracts, no contract type shall be used unless the proposed contractor's accounting system will permit timely development of all necessary cost data in the form required by the specific contract type contemplated and that the contractor's accounting system is adequate to allocate costs in accordance with generally accepted accounting principles. All cost-reimbursement type contracts shall contain a provision that only costs determined to be allowable, in accordance with established cost principles as defined in the regulations, will be reimbursable.