Problem \#3- Periodic Inventory Valuation Elsa's Boards sells a snowboard, Xpert, that is popular with snowboard enthusiasts. Information relating to Elsa's purchases of Xpert snowboards during September is shown below. During the same month, 91 Xpert snowboards were sold. Elsa's uses a periodic inventory system. Date instructions (a) Compute the ending inventory at September 30 and cost of goods sold using the FIFO, LIFO, and Average Cost Method. Prove the amount allocated to the cost of goods sold under each method. (b) For both FIFO, LIFO, and Average Cost Method, calculate the sum of ending inventory and cost of goods sold. (c ) What do you notice about the answers you found for each method