Department B had $3,000$ units in work in process that were $25\%$ completed at the beginning of the period at a cost of $$12,500,13,700$ units of direct materials were added during the period at a cost of $$28,700,15,000$ units were completed during the period, and $1,700$ units were $95\%$ completed at the end of the period. All materials are added at the beginning of the process. Direct labor was $$32,450,$ and factory overhead was $$18,710.$

The number of equivalent units of production for the period for materials, if the firstin, first$-$out method is used to cost inventories, was

$x$ a$.12,000$

b$.16,700$

c$.1,700$

d$.13,700$