Sabrina Co. uses a periodic inventory system. Its records show the following for the month of May, in which 68 units were sold. Instructions : a) Compute the ending inventory at May 31 and cost of goods sold using the FIFO and average-cost methods. b) Prove the amount allocated to cost of goods sold under each method. (Round all unit cost calculations for the average-cost method to the nearest cent and total cost to the nearest euro