Current Attempt in Progress Waterway Co. uses a periodic inventory system. Its records show the following for the month of May, in which 75 units were sold. Compute the ending inventory at May 31 and cost of goods sold using the FIFO and LIFO methods. Current Attempt in Progress Waterway Co. uses a periodic inventory system. Its records show the following for the month of May, in which 75 units were sold. Compute the ending inventory at May 31 and cost of goods sold using the FIFO and LIFO methods