The debits to Work in Process--Assembly Department for April, together with data concerning production, are as follows: Work in process, April 1, 3,000 units: Direct materials cost, for 3,000 units $ 7,200 Conversion costs, for 3,000 units, 60% completed $ 6,000 Direct materials added during April, 10,000 units $ 25,000 Conversion costs during April $ 35,750 Goods finished during April, 12,000 units --- April 30 work in process, 1,000 units, 40% completed --- All direct materials are placed in process at the beginning of the process and the first-in, first-out method is used to cost inventories. The direct materials cost per equivalent unit for April is: a) $2.50 per unit b) $5.25 per unit c) $2.08 per unit d) $2.40 per unit