Department A had 5,000 units in work in process that were 61% completed as to labor and overhead at the beginning of the period, 33,500 units of direct materials were added during the period, 36,000 units were completed during the period; and 2,500 units were 38% 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. 36,000

b. 33,500

c. 38,500

d. 31,000