I need help with the perpetual average

Ferris Company began 2016 with 4,000 units of its principal product. The cost of each unit is $8. Merchandise transactions for the month of January 2016 are as follows: rchases Date of Purchase Jan. 10 Jan. 18 Unit Units Cost Total Cost 3,000 $ 9 $27000 4,000 10 40,000 Totals 7000 $67,000 Includes purchase price and cost of freight. Sales Date of Units Sale 2,000 1,000 Jan. 20 3,000 Jan. 5 Jan. 12 Total 6,000 5,000 units were on hand at the end of the month. Required: Calculate January's ending inventory and cost of goods sold for the month using each of the following alternatives