You are estimating a company's weighted average cost of capital $($WACC$).$ The company has a debt$-$to$-$equity ratio, D$/$E of $1\mathrm{.}0,$ which means that the company has the same amount of debt and equity values $($D$/$E $=1->$ D $=$ E$).$ The required rate of return on the company's stock is $15\%.$ The yield to maturity of the company's outstanding bonds is $6\%.$ The company is subject to a $21\%$ income tax rate. What is the company's WACC in percentage $(\%)?$

Hint: You can assume any value for the equity $($or debt, but not both$).$ For example, you can set the equity value E $=1$ to determine the value for D and V$.$

Note: Write your answer in $\%$ terms $($do not round$).$ For example, write $2\mathrm{.}54(\%)$ instead of $0\mathrm{.}0254.$