Estimate the beta for only one of the stocks above (choose AAPL or CTC-A.TO). In order to do so, use monthly returns for the AAPL or CTC-A.TO calculated in part 1 above. In addition, retrieve the values of market portfolio: use S&P 500 index (ticker symbol ^GSPC). Using monthly levels of the S&P 500 index, compute monthly holding period returns for market portfolio (see calculating holding period returns for CTC-A.TO and AAPL in part 1). Estimate beta for chosen stock (CTC-A.TO or AAPL), by running the regression of this stocks monthly excess returns1 on the market portfolio excess returns (In Excel go to Tools/Data Analysis/Regression; make sure that Data Analysis add-in is installed on your computer). Is the beta positive, negative? Is it statistically different from zero? How can you tell (why)?