Using the data in the following$$ table, and the fact that the correlation of A and B is $0\mathrm{.}48,$ calculate the volatility$($standard deviation$)$ of a portfolio that is $70\%$ invested in stock A and $30\%$ invested in stock B$.($Click on the following icon in order to copy its contents into a$$ spreadsheet.$)$

Realized Returns

Year

Stock A

Stock B

$2008$

negative $10\%$

$21\%$

$2009$

$20\%$

$30\%$

$2010$

$5\%$

$7\%$

$2011$

negative $5\%$

negative $3\%$

$2012$

$2\%$

negative $8\%$

$2013$

$9\%$

$25\%$