the debt-related tax benefits implicitly simply by discounting the unlevered cash flows at the WACC. However, this approach assumes that the firm is able and willing to maintain the leverage ratio at L = B / V by issuing more debt when times are "better" than expected and retiring debt when times are "worse" than expected, with any other debt policy, the periodic debt transactions are either partially or conpletely exogenous with respect to realized market values and, consequently, the leverage ratio will not be constant except by chance. Equations (21) and (22) show that the cost of equity in any given period is a function of that period's leverage ratio. Thus, we cannot determine the cost of equity until we know the leverage ratio,