Suppose that Spencer Industries$$ capital structure features $63$ percent equity, $7$ percent preferred stock, and $30$ percent debt. Assume the before$-$tax component costs of equity, preferred stock, and debt are $11\mathrm{.}60$ percent, $9\mathrm{.}50$ percent, and $9$ percent, respectively.

What is Spencer$$s WACC if the firm faces an average tax rate of $21$ percent and can make full use of the interest tax shield?