Checkers uses the periodic inventory system. For the current month, the beginning inventory consisted of $7200$ units that cost $$12$ each. During the month, the company made two purchases: $3000$ units at $$13$ each and $12000$ units at $$13\mathrm{.}50$ each. Checkers also sold $12900$ units during the month. If the average$-$cost method is used, what is the amount of cost of goods sold for the month?