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	$7,400
Conversion costs, 3,000 units, 50% completed	5,800
Materials added during May, 10,000 units	25,900
Conversion costs during May	31,700
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.$2.25

b.$2.59

c.$3.17

d.$3.91