Trey Monson starts a merchandising business on December $1$ and enters into the following three inventory purchases. Monson uses a periodic inventory system. Also, on December $15,$ Monson sells $30$ units for $$25$ each. Of the units sold, $16$ are from December $7$ purchase and $14$ are from the December $14$ purchase. Determine the costs assigned to ending inventory when costs are assigned based specific identiciation.