the units of an item available for sale during the year were as follows: jan. 1 inventory 1,000 units at $120 feb. 17 purchase 1,375 units at $128 july 21 purchase 1,500 units at $136 nov. 23 purchase 1,125 units at $140 there are 1,200 units of the item in the physical inventory at december 31. the periodic inventory system is used. determine the inventory cost by (a) the first-in, first-out method; (b) the last-in, first-out method; and (c) the weighted average cost method.