The units of an item available for sale during the year were as follows: There are 50 units of the item in the physical inventory at December 31 . The periodic inventory system is used. a. Determine the ending inventory cost using the first-in, first-out method. 9 b. Determine the ending inventory cost using the last-in, first-out method. 4 c. Determine the ending inventory cost using the weighted average cost method. $