Question: 90 During the audit of a construction contract, it was discovered that the contractor was being paid for each ton of dirt removed. The contract called for payment based on cubic yards removed. Which internal control might have prevented this error? A. Comparison of actual costs with budgeted costs. B. Extension checks of invoice amounts. C. Comparison of invoices with purchase orders or contra: Answer (C) is correct. The contractor's invoice would have stated a unit of me from that in the contract. Thus, a comparison of the inv: original contract would have disclosed the error. D. Comparison of invoices with receiving reports