I need help finding the standard deviations!

Problem 8-07 You are considering two stocks and have determined the following information: Stock A Return Probability of the Return 29% 30 % 15 35 6 35 Stock B Return Probability of the Return 27 % 20% 18 55 8 25 a. Which of the two stocks has the higher expected return? Round your answers to two decimal places. The return on Stock A: 16.05 % The return on Stock B: 17.3 % Stock BV has the higher expected return. b. Which stock is riskier? Do not round intermediate calculations. Round your answers to two decimal places. Standard deviation of Stock A: 3 Standard deviation of Stock B: 5 Stock Av is riskier. c. Given your answers to the two previous questions, what stock is preferred? Stock BV is preferred