Which of the following costs is a mixed cost? O A Salary of a factory supervisor O B. Electricity costs of 52 per kilowatt-hour OC. Rental costs of 55,000 per month plus 5.30 per machine hour of use OD. Straight-line depreciation on factory equipment QUESTION 4 As production increases, what should happen to the fixed costs per unit? O A Stay the same O B. Increase OC. Decrease OD. Either increase or decrease, depending on the variable costs. QUESTION 5 if sales are 5820,000, variable costs are 62% of sales, and operating income is $260,000, what is the contribution margin ratio? O A 53.1% B.38 O C.62% OD 32% QUESTION 6 Salter Inc's unit selling price is $50, the unit variable costs are $35. fixed costs are $125,000, and current sales are 10,000 units. How much will operating income change if sales increase by S.000 units? O A 5150.000 decrease 8.5175,000 increase OC.575.000 increase 0.5150,000 increase