The debits to Work in Process-Assembly Department for May, together with data concerning production, are as follows: May 1, work in process: Materials cost, 3,000 units $7,900 Conversion costs, 3,000 units, 50% completed 6,000 Materials added during May, 10,000 units 26,700 Conversion costs during May 30,900 0 Goods finished during May, 11,500 units 0 May 31 work in process, 1,500 units, 50 % 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 materials cost pe for May is a. $2.67 b. $3.09 C. $2.32 d. $3.88