RealCoin Inc, a U$.$S$.$ company, is currently funded entirely by equity. RealCoin has a beta of $1\mathrm{.}6$ and a cost of equity of $12\%$ per annum. The market risk premium is $6\%$ per annum and the risk$-$free rate is $4\%$ per annum. It is considering taking on some debt which will result in a D$/$E ratio is $0\mathrm{.}5.$ It can issue this debt at before$-$tax rate of $9\%$ per annum. RealCoin pays tax at $35\%.$ Assuming that RealCoin issues new debt as planned, its new cost of capital can be estimated to be closest to which of the following? $($round to the nearest $2$ digits.$)$

a$)9\mathrm{.}95\%$

b$)10\mathrm{.}50\%$

c$)11\mathrm{.}05\%$

d$)13\mathrm{.}10\%$

e$)$ None of the other answers is correct.