In the Notation of the Book,K = (1 - $\lambda$ )K_l

In the notation of the book,K = (1 - $\lambda$ ) K_l + $\lambda$ (1 - $\lambda$ ) i Which of these are correct?

A) The debt-to-equity ratio is $\lambda$
B) The tax rate is $\tau$
C) The after-tax cost of debt capital is i
D) All of the above