Obtain Consumer Price Index (CPI) from either Quandl or FRED. \ \ - By using pdfetch or quantmod packages, obtain "monthly" S&P 500 Price Index. (or transform the series to monthly by collapse() command)\ \ - Combine these two series together monthly, start and end dates should be the same. (You can use Excel file if it is easier, then import to R)\ \ - Calculate the real value of S &P 500 Price Index.\ \ - Compare the nominal value and real value of the index. Plot them together to see visually. Is there any significant difference you can see visually? Explain why.\ \ - Forecast the real value of S&P 500 Price Index for the next 6 months.\ \ - Would you prefer to invest in the index based on the forecasted value? \ \ - Calculate the return of nominal S&P 500 Price Index. Plot the return and command on what you see visually. Does it look stationary? Forecast for the next 6 month ahead by any model you would choose? Explain the data and forecasted values.