When multiple production department rates are used to apply overhead to products, a. only fixed overhead costs are first directly traced to support and production departments and then support department costs are allocated to production departments b. support department costs are allocated to production departments and then all overhead costs are directly traced to support and production departments c. all overhead costs are first directly traced to support and production departments and then support department costs are allocated to production departments d. all manufacturing costs are first directly traced to support and production departments and then support department costs are allocated to production departments