$1.$ Which of the following statements is correct for a company with both debt and equity in its capital structure?

a$.$ WACC calculations should be based on the before$-$tax costs of all the individual capital components.

b$.$ Flotation costs associated with issuing new common stock normally reduce the WACC.

c$.$ If a company's tax rate increases, then, all else equal, its after$-$tax cost of debt will decline.

d$.$ An increase in the risk$-$free rate will normally lower the marginal costs of both debt and equity financing.

e$.$ A change in the percent of debt in a company$$s capital structure will not affect its WACC.