checkers uses the periodic inventory system. for the current month, the beginning inventory consisted of 7,200 units that cost $12 each. during the month, the company made two purchases: 3,000 units at $13 each and 12,000 units at $13.50 each. checkers also sold 12,900 units during the month. using the average cost method, what is the amount of cost of goods sold for the month? a) $167,055 b)$173,700 c)$161,850 d)$167,700