During the fiscal year 2012, the U.S. Postal Service experienced a record $15.9 billion in losses. In an effort to respond to this financial crisis, the postal service is considering closing many post office facilities that are operating at a loss. To help with this decision, suppose post office authorities would like to forecast the number of pieces of mail to be handled during 2013. Data in the Excel file postal service.xlsx show the number of pieces of mail, in billions, delivered by the U.S. Postal Service between 1983 and 2012.

Based on: U.S. Postal Service data.

a. Construct a graph showing the number of pieces of mail delivered over time.

b. Forecast the number of pieces of mail to be delivered during 2013 using a trend projection.

c. Check the forecasting model in part b for the presence of autocorrelation using a = 0.05.

d. Comment on the appropriateness of using trend projection for these data.AppendixLO1