PLEASE answer ALL parts of the question

Month Cola Co. Gas Co. -0.0210 0.0280 January February 0.0000 -0.0050 -0.0180 March -0.0200 0.0090 0.0280 April May -0.0310 0.0840 June -0.0840 -0.0460 -0.1190 0.0820 July August -0.0160 0.0460 -0.0160 0.0460 August September 0.0550 0.0300 October -0.0110 0.0140 November -0.0380 0.0290 December -0.0220 0.0740 The following table contains monthly returns for Cola Co. and Gas Co. for 2013 (the returns are shown in decimal form, i.e., 0.035 is 3.5%). Using this table and the fact that Cola Co. and Gas Co. have a correlation of - 0.0969, calculate the volatility (standard deviation) of a portfolio that is 60% invested in Cola Co. stock and 40% invested in Gas Co. stock. Calculate the volatility by: a. Using the formula: Var(Ro) = w; SD (R4)2 + w SD (R2) + 2W, W2 Corr (R1,R2) SD SD (R1) SD (R2) b. Calculating the monthly returns of the portfolio and computing its volatility directly. c. How do your results compare