The following table contains monthly returns for Cola Co$.$ and Gas Co$.$ for $2022$: B:$.$ Using this table and the facts that Cola Co$.$ has a standard deviation of return of $4\mathrm{.}37\%,$ Gas Co$.$ has a standard deviation of return of $3\mathrm{.}97\%,$ and they have a correlation of $-0\mathrm{.}0969,$ calculate the volatility $($standard deviation$)$ of a portfolio that is $70\%$ invested in Cola Co$.$ stock and $30\%$ invested in Gas Co$.$ stock.

a$.$ Calculate the volatility using the formula:

Var $($Rp$)=$ wCola SD $($Rcola$)2+$ was SD $($RGas$)2+2$

$($already answered, votality is $3\mathrm{.}17\%)$

b$.$ Calculating the monthly returns of the portfolio and computing its volatility directly.

c$.$ How do your results compare?