1. Find the best autoregressive model for the closing price of the S&P 500 using the Excel file S&P 500. 2. Find the best autoregressive model for each of the variables in the Excel file Retail Electricity Prices 3. Develop a multiple regression model with categorical variables that incorporate seasonality for forecasting the temperature in Washington, D.C., using the data for years 1999 and 2000 in the Excel file Washington DC Weather. Use the model to generate forecasts for the next nine months and compare the forecasts to the actual observations in the data for the year 2001.