Please show formulas and calculations

Question $12(2$ points$)$

Here are the expected returns on two stocks:

If you form a $60-40$ portfolio of the two stocks $(60\%$ of $x$ and $40\%$ of $Y),$ what is the

portfolio's standard deviation?

$8\mathrm{.}10\%$

$9\mathrm{.}26\%$

$9\mathrm{.}69\%$

$6\mathrm{.}90\%$

$12\mathrm{.}99\%$