I have tried to do the accounting homework problem and don't understand how to do the FIFO method. The problem states the following:

Trey Monson starts a merchandising business on December 1 and enters into the following three inventory purchases. Also, on December

15, Monson sells 10 units for $50 each.

Purchases on December 7 - 8 units @ $20 cost

Purchases on December 14 - 17 units @ $30 cost

Purchases on December 21 - 15 units @ $36.00 cost

Required:

Monson uses a perpetual inventory system. Determine the costs assigned to the December 31 ending inventory based on the FIFO method.