A company has a financial structure where equity is $70\%$ of its total debt plus equity. Its cost of equity is $10\%$ and gross loan interest is $5\%.$ Corporation tax is paid at $30\%.$ What is the company$$s weighted average cost of capital $($WACC$)?$

a$.$

$8\mathrm{.}05\%$

b$.$

$7\mathrm{.}80\%$

c$.$

$8\mathrm{.}70\%$

d$.$

$7\mathrm{.}55\%$