Which of the following statements is true of operating leverage? Oa. It is the difference between price and unit variable cost. Ob. It is the ratio of total contribution margin to sales or of unit contribution to price. Oc. It shows how far a company's actual sales and/or units are above or below the break-even point. Od. Oe. None of these choices are correct. It is the use of fixed costs to increase the percentage changes in profits as sales activity changes