Vafeas Inc.'s capital structure consists of 80% debt and 20% common equity, its beta is 1.60, and its tax rate is 35%. However, the CFO thinks the company has too much debt, and he is considering moving to a capital structure with 40% debt and 60% equity. The risk-free rate is 5.0% and the market risk premium is 6.0%. By how much would the capital structure shift change the firm's cost of equity? a. -5.20% b. -5.78% c. -6.36% d. -6.99% e. -7.69%