please help with excel step-by-step (detailed) much appreciated **IMPORTANT** PLEASE MAKE SURE TO USE EXCEL WITH FORMULAS

BAE Inc. is trying to estimate its optimal capital structure. Right now, Bob has a capital structure that consists of 20% debt and 80% equity, based on market values. (Its D/S ratio is 0.25.) The risk-free rate is 6% and the market risk premium is 5%. Currently the companys cost of equity, which is based on the CAPM, is 12% and its tax rate is 40%. What would be Bob's estimated cost of equity if it were to change its capital structure to 50% debt and 50% equity?

• A. 13.30%
• B. 14.72%
• C. 15.60%
• D. 14.35%
• E. 13.00%

PLEASE HELP WITH EXCEL STEP-BY-STEP (IN FULL detail) much appreciated **IMPORTANT** I WANT TO LEARN