Oak Tree Ltd. Inventory records for a particular development program show the following at October 31, 2016: Oct 1 Beginning inventory 15 Purchase 26 Purchase 10 units @ 60 units @ 70 units @ $0.60 = 0.65= 0.70= $6 39 49 At October 30, sold 120 units of these programs. Oak Tree Ltd. uses the perpetual inventory system. Compute cost of goods sold and ending inventory, using each of the following methods: Specific unit cost. Weighted-average cost First-in, first out cost Which method produces the highest cost of goods sold? Which method produces the lowest cost of goods sold? What causes the difference in cost of goods sold?