The debits to Work in Process$$Assembly Department for May, together with data concerning production, are as follows:

May $1,$ work in process:

Line Item Description Amount

Materials cost, $3,000$ units $$8,600$

Conversion costs, $3,000$ units, $66\mathrm{.}7\%$ completed $5,700$

Materials added during May, $10,000$ units $26,900$

Conversion costs during May $33,500$

Goods finished during May, $11,500$ units $$

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 per equivalent unit for May is

a$.$ $$2\mathrm{.}34$

b$.$ $$4\mathrm{.}21$

c$.$ $$3\mathrm{.}35$

d$.$ $$2\mathrm{.}69$