Trey Monson starts a merchandising business on December 1 and enters into three inventory purchases: Purchases on December 7 10 units @ $ 6.00 cost Purchases on December 14 20 units @ $12.00 cost Purchases on December 21 15 units @ $14.00 cost Monson sells 15 units for $20 each on December 15. Assume the periodic inventory system is used. Determine the costs assigned to the December 31 ending inventory when costs are assigned based on FIFO