(The following data is used in questions 14 through 16) Biff Inc., a national wholesaler, provided the following information for the month of September: Sales price per unit $600 per unit Units sold 275 Merchandise inventory, beginning balance $27,000 Merchandise inventory, ending balance $35,000 Purchases of merchandise inventory $72,000 Property taxes on corporate office $14,000 $9,000 Advertising expense Administrative expense The net operating income for September was: $53 per unit