Department A had 4,200 units in work in process that were 80% completed as to labor and overhead at the beginning of the period, 36,800 units of direct materials were added during the period, 38,100 units were completed during the period; and 2,900 units were 35% completed as to labor and overhead at the end of the period. All materials are added at the beginning of the process. The first-in, first-out method is used to cost inventories. The number of equivalent units of production for material costs for the period was a. 38,100 b. 33,900 c. 36,800 d. 41,000