Trey Monson starts a merchandising business on December 1 and enters into the following three inventory purchases. Also, on December 15, Monson sells 30 units for $25 each. Purchases on December 7 20 units @ $10.00 cost Purchases on December 14 36 units @ $15.00 cost Purchases on December 21 30 units @ $18.00 cost Required: Monson uses a perpetual inventory system. Determine the costs assigned to the December 31 ending inventory based on the FIFO method