Department F had $4,000$ units in Work in Process that were $40\%$ completed at the beginning of the period at a cost of $$12,900.$ Of the $$12,900,$ $$8,500$ was for material and $$4,400$ was for conversion costs. $14,000$ units of direct materials were added during the period at a cost of $$26,800,15,000$ units were completed during the period, and $3,000$ units were $75\%$ completed at the end of the period. All materials are added at the beginning of the process. Direct labor was $$34,000$ and factory overhead was $$18,600.$

If the average cost method is used, the conversion cost per unit $($to the nearest cent$)$ would be

a$.$ $$3\mathrm{.}17$

b$.$ $$3\mathrm{.}80$

c$.$ $$3\mathrm{.}30$

d$.$ $$5\mathrm{.}18$