Department M had $2,000$ units $40\%$ completed in process at the beginning of June, $12,000$ units completed during June, and $1,200$ units $25\%$ completed at the end of June. The number of equivalent units of production for conversion costs for June if the first$-$in$,$ first$-$out method is used to cost inventories is

a$.11,200$ units

b$.11,500$ units

c$.15,200$ units

d$.10,000$ units