Please show all work on excel

Cartwright Communications is considering making a change to its capital structure to reduce its cost of capital and increase firm value. Right now, Cartwright has a capital structure that consists of 20% debt and 80% equity, based on market values. (Its D/E ratio is 0.25.) The risk-free rate is 6% and the market risk premium, r_M r_RF, is 5%. Currently the company's cost of equity, which is based on the CAPM, is 12% and its tax rate is 40%.

1. What would be Cartwright's estimated cost of equity if it were to change its capital structure to 50% debt and 50% equity?