How to figure out this kind of question?It is difficult for me. Thank you~

The following table contains monthly returns for Cola Corporation and Gas Corporation for 2012: g (The returns are shown in decimal form. i.e., 0035 is 3.5%.) Using this table and the fact that Cola Corporation and Gas Corporation have a correlation of 0.0969. calculate the volatility (standard deviation) of a portfolio that is 50% invested in Cola Corporation shares and 50% invested in Gas Corporation shares Calculate the volatility by I. using the [allowing lormula, V8I(Rp) = w: SD (R1) 2 + w; SD(R2) + 2W1W2 Corr(R1,R2)SD(R1)SD(R2) , and b. Illoulating the monthly returns of the portfolio and computing its volatility diredly, c. How do your results compare