please explain

Chazen Company's inventory balance at the beginning of the year was $8,400. During the year, the company had Purchases of $54,000 and Purchases Returns and Allowances of $4,400. The company's inventory balance at the end of the year is $6,400. Compute cost of goods sold for the year assuming Chazen uses the periodic inventory system. $ 8,400 54,000 4,400 Beginning inventory Purchases Less: Purchases returns and allowances Cost of goods available for sale Less ending inventory Cost of goods sold 6,400