Department A had 4,600 units in work in process that were 63% completed as to labor and overhead at the beginning of the period; 33,600 units of direct materials were added during the period; 36,000 units were completed during the period; and 2,200 units were 21% 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.33,600

b.31,400

c.36,000

d.38,200