Florida Company $($FC$)$ and Minnesota Company $($MC$)$ are both service companies. Their stock returns for the past three years were as follows: FC: $5$ percent, $15$ percent, $20$ percent; MC: $8$ percent, $8$ percent, $20$ percent. What is the standard deviation of a portfolio with $50$ percent of the funds invested in FC and $50$ percent in MC$?($Ignore the correction for the loss of a degree of freedom set out in the text.$)$

Multiple Choice

$10\mathrm{.}6$ percent

$14\mathrm{.}4$ percent

$9\mathrm{.}3$ percent

$7\mathrm{.}6$ percent