(b) Disbursing officers are those officials designated to make payments under a contract or to receive payments of amounts due under a contract. The disbursing officer is responsible for determining the amount and collecting contract debts whenever overpayments or erroneous payments have been made. The disbursing officer also has primary responsibility when the amounts due and dates for payment are contained in the contract, and a copy of the contract has been furnished to the disbursing officer with notice to collect as amounts become due.