Hamada Company uses the FIFO method in its process costing system. Beginning inventory in the mixing department consisted of 4,000 units, 75% complete with respect to conversion costs. Ending work in process inventory consisted of 3,000 units, 60% complete with respect to conversion costs. If 12,000 units were transferred to the next department during the period, the equivalent units for conversion costs would be: .a 10,800 units .b 13,200 units 12,000 units .d 13,000 units