4--Joel's Blender Company sold 4 000 blenders in October at a sales price of $35 each. Joel's variable cost is $15 per blender. Calculate Joel's total contribution margin. 5--Makenzie's Coffee Importers sold 4 000 items in October at a sales price of $40 per item. Makenzie's variable cost per item is $15 per item. Makenzie's monthly fixed costs are $10 000. Determine Makenzie's operating income for October. 6--Provide some real world examples of both variable and fixed costs. Why did you classify these costs in this way