The debits to Work in ProcessAssembly Department for May, together with data concerning production, are as follows: May 1, work in process: Materials cost, 3,000 units $8,800 Conversion costs, 3,000 units, 50% completed 5,700 Materials added during May, 10,000 units 25,600 Conversion costs during May 31,900 Goods finished during May, 11,500 units 0 May 31 work in process, 1,500 units, 50% completed 0 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 May is

a.$3.19 b.$2.23 c.$2.56 d.$4.07