Shawhan Supply plans to maintain its optimal capitalstructure of 30% debt 20% pr

Shawhan Supply plans to maintain its optimal capitalstructure of 30% debt 20% preferred stock and 50% common stockfar into the future. The required return on each component is:debt10%; preferred stock11%; and common stock18%. Assuming a 40%marginal tax rate what after-tax rate of return must ShawhanSupply earn on its investments if the value of the firm is toremain unchanged?