please write formula & explain your answer

please type the answer will be better for me, thankyou Gent Company uses a periodic inventory system. For May, when the company sold 530 units, the following information is available: Unit costs Units 370 7 May 1 inventory May 19 purchase May 29 purchase 9 400 410 1 180 11 Instruction: Compute the May 31 inventory and the May cost of goods sold using: a) the average-cost method (55 points) b) FIFO method (45 points)