$1.)$ Definitions:

a$.$ The expected return on debt; if the debt has very low default risk, this is close to its yield to maturity.

b$.$ The expected return on equity

c$.$ A weighted average of the cost of equity and the cost of debt, where the weights are the relative market values of the firm$$s debt and equity.

d$.$ Equity Beta $-$ The change in the return of the stock for each additional $1\%$ change in the market return.

e$.$ The change in the return on a portfolio of all the firm$$s securities $($debt and equity$)$ for each additional $1\%$ change in the market return.

f$.$ A company specializing in one activity that is similar to that of a division of a more diversified company.