Download Aug 2015- Aug 2020 monthly stock prices of Pfizer and compute the corresponding stock returns, their average and standard deviation, annualised. Do the same for the S&P500 and for Apple Inc. a) Using the S&P500 as a proxy for the market portfolio, compute the market beta of the two companies and measure their diversifiable risk, expressed as a percentage. (b) Build an equally weighted portfolio of the two companies and compute its expected return and standard deviation. Comment on the results. The stock prices can be downloaded from Yahoo Finance