Contribution Margin United Merchants Company sells 18,000 units at $13 per unit. Variable costs are $8.58 per unit, and fixed costs are $13,000 Determine (a) the contribution margin ratio, (b) the unit contribution margin, and (c) income from operations. a. Contribution margin ratio (Enter as a whole number.) % b. Unit contribution margin (Round to the nearest cent.) per unit Income from operations