Department E had 4,000 units in Work in Process that were 40% completed at the beginning of the period at a cost of $12,500, 14,000 units of direct materials were added during the period at a cost of $28,700, 15,000 units were completed during the period, and 3,000 units were 75% completed at the end of the period. All materials are added at the beginning of the process. Direct labor was $32,450 and factory overhead was $18,710.

The number of equivalent units of production for the period for materials if the weighted average method is used to cost inventories was?

Break this down simply please.