Download to a spreadsheet the last three years of monthly adjusted stock prices for Coca-Cola (KO), Citigroup (C), and Pfizer (PFE). a. Calculate the monthly returns. b. Calculate the monthly standard deviation of those returns (Use the Excel function STDEV.S). Find the annualized standard deviation by multiplying by the square root of 12. c. Use the Excel function CORREL to calculate the correlation coefficient between the monthly returns for each pair of stocks. Which pair provides the greatest gain from diversification? d. Calculate the standard deviation of returns for a portfolio with equal investments in the three stocks.