The debits to Work in Process-Assembly Department for April, together with data concerning production, are as follows: 27. April 1, work in process: Materials cost, 3,000 units Conversion costs, 3,000 units, s 7,500 2/3 completed Materials added during April, 10,000 units Conversion costs during April Goods finished during April, 11,500 units April 30 work in process, 1,500 units, 6,000 26,000 31,000 1/2 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 per equivalent unit for April is: a. $2.60 b. $2.26 c. $2.50 d. $5.50