Ruth's Boards sells a snowboard, Xpert, that is popular with snowboard enthusiasts. Information relating to Ruth's purchases of Xpert snowboards during September is shown below. During the same month, 120 Xpert snowboards were sold. Ruth's uses a periodic inventory system. (a) Compute the ending inventory at September 30 and cost of goods sold using the FIFO and LIFO methods. For both FIFO and LIFO, calculate the sum of ending inventory and cost of goods sold