Department $S$ had $500$ units $60\%$ completed in process at the beginning of the period, $8,500$ units completed during the period, and What was the number of equivalent units of production for the period for conversion if the first$-$in$,$ first$-$out method is used to cost inve to both direct materials and conversion cost.

a$.8,200$

b$.8,500$

c$.9,500$

d$.8,000$