(b) Calculate the cost of goods sold for May and the ending inventory at May 31 using the average cost formula. (For average, use 3 decimal places, e.g. 15.235 in your calculations and round final answers to 2 decimal places, e.g 5.25.) Cost of goods sold $ Ending Inventory Sheffield Inc. uses a perpetual inventory system. Its records show the following for the month of May. Unit Cost Date Units Total Cost $224 1 Explanation Inventory Purchase 28 May May $8 15 26 9 234 May 18 Sale (49) May 24 Purchase 39 10 3007 Total 44 $848