how do youget this anser

4. Gerald's Department Store is a merchandising company that uses the periodic inventory system. Selected account balances are listed below: Sales Purchases Inventory (Beginning) Inventory (Ending) Purchase returns and allowances Purchase discounts Transportation-in Sales discounts Sales returns and allowances $175.000 90,000 23,000 17,000 3.000 7.000 4.000 8.000 5.000 Gerald's gross profit is: a) $68,000 b) $72,000 c) $78,000 d) $85.000 e) Not determinable from the information given