4. Herrera Corporation has provided the following contribution format income statement. All questions concern situations that are within the relevant range. Sales (8,000 units) Variable expenses Contribution margin Fixed expenses Net operating income a. What is the contribution margin per unit? $480,000 336,000 144,000 142.200 $ 1.800 b. What is the break-even point in dollar sales? c. How many units must be sold to achieve a target profit of $50,400? d. What is the margin of safety percentage? e. Compute Herrera's operating leverage. f. What is the estimated percent increase in net operating income that would result from a 15% increase in sales? Use your computation of operating leverage to answer this