how to solve part 4

Attempt 5/10 for 10 pts. Part 4 What was the annual standard deviation of portfolio returns? 3+ decimals Submit Problem 19 Intro The table below shows the historical rates of return (including dividends) for two stocks: Year Stock A Stock B 2020 4% -3% 2019 12% 20% 2018 8% 20% 2017 -12% 4% Stock A makes up 50% of the value of portfolio, and stock B makes up the rest. Calculate the portfolio return for each year