Jet Black Products uses a periodic inventory system. For 2018 and 2019, Jet Black has the following data:

All purchases and sales are for cash.
Required:
1. Compute cost of goods sold, the cost of ending inventory, and gross margin for each year using FIFO.
2. Compute cost of goods sold, the cost of ending inventory, and gross margin for each year using LIFO.
3. Compute cost of goods sold, the cost of ending inventory, and gross margin for each year using the average cost method.
4. Which method would result in the lowest amount paid for taxes?
5. Which method produces the most realistic amount for income? For inventory? Explain your answer.
6. What is the effect of purchases made later in the year on the gross margin when LIFO is employed? When FIFO is employed? Be sure to explain why any differences occur.
7. If you worked Problem 6-68A, compare your answers. What are the differences? Be sure to explain why any differences occurred.