Following are costs for eight different items. Costs are shown for three different levels of units produced and sold. Classify each of the eight cost items as either variable, fixed, or mixed. Costs for Different Levels of Units Produced and Sold At 0 units At 2,000 units At 4,000 units Direct labor $ 0 $ 13,800 $ 27,600 Depreciation on factory equipment 6,800 6,800 6,800 Direct materials 0 9,800 19,600 Rent on factory building 4,800 4,800 4,800 Salesperson compensation 6,800 6,800 7,800 Factory supervisor salary 7,800 7,800 7,800 Factory utilities 480 880 1,080 Insurance on factory building 1,750 1,750 1,750