Marwick's Pianos, Incorporated, purchases pianos from a large manufacturer for an average cost of $1,507 per unit and then sells them to retail customers for an average price of $2,900 each. The company's selling and administrative costs for a typical month are presented below: Costs Selling: Advertising Sales salaries and commissions Delivery of pianos to customers utilities Depreciation of sales facilities Admindstrative: sxecutive salaries Insurance Clerical Depreciation of office equipment Cost Formula $ 940 per month $4,789 per month, plus 48 of sales $63 per piano sold $660 per month $5,041 per month $13,493 per month $718 per month $2,454 per month, plus $37 per piano sold $945 per month During August, Marwick's Pianos, Incorporated, sold and delivere