How to slove?

Problem 6-4A The management of Gresa Inc. is reevaluating the appropriateness of using its present inventory cost flow method, which is average-cost. The company requests your help in determining the results of operations for 2017 if either the FIFO or the LIFO method had been used. For 2017, the accounting records show these data Purchases and Sales Total net sales (260,000 units) Total cost of goods purchased (270,000 units) 1,287,000 698,000 $16,000 Beginning (8,000 units) Ending (18,000 units) Purchases were made quarterly as follows. Quarter Units Unit Cost Total Cost $2.40 168,000 2.50 150,000 2.60 156,000 2.80 224,000 $698,000 70,000 60,000 60,000 80,000 270,000 Operating expenses were $150,000, and the company's income tax rate is 40%