MPJ Corp. has determined that it should work to create an optimal capital structure which is composed of the following sources, their costs $($pre$-$tax when applicable$)$ and target proportions:

Long$-$term Debt, rd $6\mathrm{.}4\%,60\%$ of capital structurePreferred Stock, rp $8\mathrm{.}5\%,10\%$ of capital structureCommon Equity, rs $13\mathrm{.}8\%,30\%$ of capital structure

MPJ Corp. has an average tax rate of $25\%$

MPJ Corp.$$s weighted average cost of capital will be:

$8\mathrm{.}17$ percent

$7\mathrm{.}78$ percent

$9\mathrm{.}13$ percent

$29\mathrm{.}70$ percent