11 Assume a firm uses job costing. Which of the following is NOT a good reason to use departmental overhead rates rather than a single plantwide rate? a. Overhead costs in some departments are a very large proportion of total department cost, but are a very small proportion in other departments. b. Total overhead costs amount to about 5 per cent of total prime costs. c. The various products made use of different sequences of manufacturing activities. Od. The firm makes multiple products using common equipment and employees