$.$ A software company is developing a project for a fair value stock valuation program, where the proposed capital structure is $60\%$ equity $($ordinary shares$)$ and $40\%$ debt. The beta coefficient $($BETA$)$ for software projects is $2,$ the risk$-$free rate of return $($Rf$)$ is $6\%,$ the market return rate $($Rm$)$ is $11\%,$ the cost of borrowing before tax is $9\%($yield to maturity $-$ YTM$),$ and the tax rate is $40\%.$ Therefore, the weighted average cost of capital $($WACC$)$ is:

$($a$)9\mathrm{.}6\%($b$)11\mathrm{.}8\%($c$)13\mathrm{.}1\%$