At the various activity levels shown, harper company incurred the following costs: units sold 20 40 60 80 100 a. rental cost per unit of merchandise sold $ 36.00 $ 18.00 $ 12.00 $ 9.00 $ 7.20 b. total phone expense 80.00 100.00 120.00 140.00 160.00 c. cost per unit of supplies 1.00 1.00 1.00 1.00 1.00 d. total insurance cost 480.00 480.00 480.00 480.00 480.00 e. total salary cost 1,200.00 1,600.00 2,000.00 2,400.00 2,800.00 f. total cost of goods sold 1,800.00 3,600.00 5,400.00 7,200.00 9,000.00 g. depreciation cost per unit 240.00 120.00 80.00 60.00 48.00 h. total rent cost 3,200.00 3,200.00 3,200.00 3,200.00 3,200.00 i. total cost of shopping bags 2.00 4.00 6.00 8.00 10.00 j. cost per unit of merchandise sold 90.00 90.00 90.00 90.00 90.00 required identify each of these costs as fixed, variable, or mixed.