Use excel to work this out and show the formula!

7-7. (Calculating expected rates of return and risk) Syntex, Inc., is considering an in- vestment in one of two common stocks. Given the information that follows, which investment is better, based on risk as measured by the standard deviation) and return? Common Stock A Probability Return 11% .40 15% .30 19% -30 .20 Common Stock B Probability Return -5% .30 6% .30 14% 20 22%