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 $8,100 5,800 Conversion costs, 3,000 units, 50% completed Materials added during May, 10,000 units 26,500 Conversion costs during May 33,600 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 Oa. $3.36 Ob. $4.17 Oc. $2.30 Od. $2.65