Department M had $2,700$ units $57\%$ completed in process at the beginning of June, $13,100$ units completed during June, and $1,500$ 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$.13,475$ units

b$.11,936$ units

c$.10,400$ units

d$.14,975$ units