Headlands Industries uses a periodic inventory system. Its records show the following for the month of May, in which 77 units were sold Date May1 Inventory 15 Explanation Units Unit Cost Total Cost 31 23 37 91 $10 $310 253 Purchase Purchase Total 12 $1,007 (b) Calculate the ending inventory at May 31 using the FIFO, LIFO and average-cost methods. (Round answers to 0 decimal places, e.g. 125.) FIFO LIFO AVERAGE-COST The ending inventory at May 31