Oak Tree Ltd. Inventory records for a particular development program show the following at October 31, 2016:

Oct 1	Beginning inventory	5 units @	$150 =	$750
15	Purchase	11 units @	160 =	1,760
26	Purchase	5 units @	170 =	850

At October 31, 10 units of these programs are on hand. Oak Tree Ltd. uses the perpetual inventory system.

Requirements:

Compute cost of goods sold and ending inventory, using each of the following methods:

Specific unit cost, with two $150 units, three $160 units, and five $170 units still on hand at the end.

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?