Department S had no work in process at the beginning of the period. It added 12,000 units of direct materials during the period at a cost of $96,000. During the period, 9,000 units were completed, and 3,000 units were 30% completed as to labor and overhead at the end of the period. All materials are added at the beginning of the process. Direct labor was $53,460, and factory overhead was $13,860. The total cost of units completed during the period was a.$72,000 b.$120,600 c.$133,200 d.$159,840