Riverside Engineering is a machine shop that uses job order costing. Overhead is applied to individual jobs at a predetermined rate based on direct labor costs. The job cost sheet for job no. 321 appears below. JOB COST SHEET JOB NUMBER: 321 DATE STARTED: May 10 PRODUCT: 2" Brass Check Valves DATE COMPLETED: May 21 UNITS COMPLETED: 4000 Direct materials used $ 7,800 Direct labor 1,500 Manufacturing overhead applied 3,000 Total cost of job no. 321 $ 12,300 Unit cost ($12,300