Trey Monson starts a merchandising business on December 1 and enters into the following three inventory purchases. Monson uses a perpetual inventory system. Also, on December 15, Monson sells 30 units for $35 each. Purchases on December? Purchases on December 14 Purchases on Decenber 21 20 units e $14.00 cost 36 units 8$21.00 cost 30 units 9$25,00 cost Required: Determine the costs assigned to the December 31 ending inventory based on the FIFO method