Department A had 4,500 units in work in process that were 66% completed as to labor and overhead at the beginning of the period, 26,500 units of direct materials were added during the period, 28,700 units were completed during the period; and 2,300 units were 39% 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. 31.000 Ob. 24200 Oc. 28.700 Od. 26.500