Therap software company is trying to determine its optimal capital structure. The company$$s current capital structure consists of $35\%$ debt and $65\%$ common equity; however, the treasurer believes that the firm should use more debt. Currently, the company$$s cost of equity capital is $9\%,$ which is determined by CAPM. What would be Therap$$s estimated cost of equity capital if they change their capital structure to $50\%$ debt? Risk$-$free rate is $3\%,$ market index returns $11\%,$ and the Therap$$s tax rate is $25\%.$