Search the internet to find the monthly stock price in 2015 for the S&P 500, Wal-Mart and Target. Put a table together with information and also state your source of information (URL used). Then calculate the average monthly holding-period returns and the standard deviation of these returns. A. Assume you want to invest half your money in Wal-Mart and half your money in Target. Calculate the average monthly holding-period return for your two stock portfolio. How does this compare to the S&P 50 average monthly holding-period return?