Levin Corporation has fixed operating costs of $72,000, variable operating costs of $6.75 per unit, and a selling price of $9.75 per unit. a. Calculate the operating break-even point in units. b. Compute the degree of operating leverage (DOL) using the following unit sales levels as a base: 25,000, 30,000, 40,000. Use the formula given in the text. c. Graph the DOL figures that you computed in part b (on the y-axis) against base sales levels (on the x-axis). d. Compute the degree of operating leverage at 24,000 units; add this point to your graph. e. What principle do your graph and figures illustrate