The beginning inventory was $60\%$ complete for materials and $20\%$ complete for conversion costs. The ending inventory was $90\%$

complete for materials and $40\%$ complete for conversion costs.

Costs pertaining to the month of May are as follows:

The beginning inventory costs are: materials, $$54,560$; direct labor, $$20,320$; and factory overhead, $$15,240.$

Costs incurred during May are: materials used, $$468,000$; direct labor, $$182,880$; and factory overhead, $$391,160.$

Using the FIFO method, the equivalent unit cost of materials for May is

$$4\mathrm{.}60$

$$4\mathrm{.}12$

$$4\mathrm{.}80$

$$4\mathrm{.}50$