Go Tro uses a periodic inventory system. At the beginning of the January 2017, inventory consisted of 2,000 units costing $8 each. On January 10, 4,500 units were purchased costing $9 each. Finally, on January 20, 3,000 more units were purchased costing $10.50 each. Unit sales consisted of 1,000 units on January 8 for $20 each, 4,000 units on January 15 for $22 each, and 1,500 units for $24 each on January 25.

a. Calculate cost of goods sold, ending inventory, and gross profit under the FIFO method.

b. Calculate cost of goods sold, ending inventory, and gross profit under the LIFO method.

c. Calculate cost of goods sold, ending inventory, and gross profit under the weighted average method.