MC algo $14-17$ D$/$E And WACC

Wentworth's Five and Dime Store has a cost of equity of $10\mathrm{.}9$ percent. The company has an aftertax cost of debt of $4\mathrm{.}6$ percent, and the tax rate is $21$ percent. If the company's debt$-$equity ratio is $\mathrm{.}70,$ what is the weighted average cost of capital?