Suppose that TNT$,$ Incorporated has a capital structure of $43$ percent equity, $23$ percent preferred stock, and $34$ percent debt. If the after$-$tax component costs of equity, preferred stock and debt are $15\mathrm{.}4$ percent, $10$ percent and $7$ percent, respectively, what is TNT$\text{'}$s WACC if the firm faces an average tax rate of $21$ percent?