What is the formula to calculate the volatility of three stocks?

using the data from Table 12.3 What is the volaility Of an equafry weighted portfolio Of Mkrosoft aryl Starbucks stock? The volatility portfolio to decimal place.) O Data TABLE 12.3 Esumated mnual and Correlations tor Selected Stocks (Based Monthly Retums, January 2015) Sta Devi. Coca.C,da McDonald's '&rosott 0.18 0.40 0.43 0.52 0.28 Starbu:ks 062 0.48 Netflix coca-cola o. 40 0.34 McDonald's 0.43 0,17 037 Cisco 0.52 0.52 26% 0.28 0.10 0.34 Authors' calcualms data Irun center Research In securlty fitc.es. Don e