Department A had 4,300 units in work in process that were 71% completed as to labor and overhead at the beginning of the period, 38,100 units of direct materials were added during the period, 39,400 units were completed during the period; and 3,000 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 Oa. 35,100 Ob. 38,100 Oc 39,400 Od. 42,400