How the purchases is 107,800 even though it is not given in the problem?

Donna Company Cost of Goods Sold Statement For the month of May, 2016 Direct materials used Materials, May 1 Purchases Total available Less>Material - May 31 Direct labor Factory overhead Total manufacturing costs Work in process, May 1 Cost of goods put into process Less: Work in process, May 31 Cost of goods manufactured Finished goods - May 1 Total goods available for sale Less: Finished goods - May 31 Cost of goods sold 124,000 107,800 231,800 115,000 116,800 160,000 240,000 516,800 129,200 646,000 124,000 522,000 150,000 672,000 122,000 550,000