Hello, please advise, thanks

Situational Software Co. (SSC) is trying to establish its optimal capital structure. Its current capital structure consists of 20% debt and 80% equity; however, the CEO believes that the firm should use more debt. The risk-free rate, RF, is 3%; the market risk premium, RPM, is 7%; and the firm's tax rate is 25%. Currently, SSC's cost of equity is 15%, which is determined by the CAPM. What would be SSC's estimated cost of equity if it changed its capital structure to 50% debt and 50% equity? Do not round intermediate calculations. Round your answer to two decimal places. %