Consider a firm that has $40\%$ of debt, $20\%$ of preferred stock, and $40\%$ of equity. The rates of return for debt, preferred stock, and equity are $5\%,10\%,$ and $18\%,$ respectively. The corporate tax rate is $36\%.$ What is the weighted average cost of capital? Enter your answer as a percentage and rounded to $2$ DECIMAL PLACES. Do not include the percentage sign in your answer.