I was able figure out the answers for FIFO and LIFO, but for some reason I can't figure out the average-cost

Marigold Corp. uses a periodic inventory system and reports the following for the month of June. Unit Cost Date Units June 1 120 $5 Explanation Inventory Purchase Purchase Inventory Total Cost $ 600 2,040 1.400 12 340 6 23 200 7 30 203 (a) - Your answer is partially correct. Compute the cost of the ending inventory and the cost of goods sold under FIFO, LIFO, and average-cost. (Round per unit cost to 3 decimal places, e.g. 15.647 and final answers to 0 decimal places, e.g. 5,125.) FIFO LIFO Average-cost Cost of the ending inventory $ 1418 $ 1098 $ Cost of goods sold $ 2622 $ 2942 $ 2744