Subject to the limitations of this Section and unless otherwise authorized by law, any type of contract that will promote the best interests of the State may be used, except that cost-plus-a-percentage-of-cost contracts are prohibited. A cost-reimbursement contract may be used only when a determination is made in writing that a cost-reimbursement contract is likely to be less costly to the State than any other type or that it is impracticable to obtain the item required except under that type of contract. The general form of contracts shall be determined by the chief procurement officer.