Florida Company $($FC$)$ and Minnesota Company $($MC$)$ are both service companies. Their stock returns for the past three years were as follows: FC: $-25$ percent, $31$ percent, $24$ percent, $MC$ : $28$ percent, $28$ percent, $40$ percent. What is the standard deviation of a portiolio 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

$20\mathrm{.}6$ percent

$16\mathrm{.}8$ percent

$13\mathrm{.}8$ percent

$12\mathrm{.}5$ percent