Jackson and Jackson Inc. has the following market values $($in millions of $$)$: debt $=9\mathrm{.}20$; preferred stock $=3\mathrm{.}30$; common stock $=11\mathrm{.}80.$ The marginal corporate tax rate is $35\%.$ Required rates of return are as follows: $5\mathrm{.}60\%$ on debt, $8\mathrm{.}00\%$ on preferred stock, and $9\mathrm{.}00\%$ on common stock. What is the weighted average cost of capital?a$\mathrm{.}8\mathrm{.}32\%$b$\mathrm{.}6\mathrm{.}20\%$c$\mathrm{.}4\mathrm{.}93\%$d$\mathrm{.}7\mathrm{.}58\%$e$\mathrm{.}6\mathrm{.}83\%$