The U.S. Federal Reserve in St. Louis stores a host of economic data on its Web site at http://research.stlouisfed.org/fred2/categories/106. Download the following time series from this Web site:

a. U.S. GNP.

b. Annual Federal Funds rate.

c. Consumer price index.

In each case, use a minimum of 50 data points over a period not including the most recent 25 years. Graph the data points, and determine first the level of differencing that appears to be required. Once you have obtained a stationary process, use the methods outlined in this section to arrive at an appropriate ARIMA model for each case. Compare the most recent 25 years of observations with the predictions obtained from your model using both one-step-ahead and two-step-ahead forecasts.