FILE Revenue passenger-miles are calculated by m ultiplying the number of paying passengers by the distance flow n in thousands. The accompanying table shows a portion of m onthly data on revenue passengermiles (in millions) from January 2006 through September 2010; the full data set can be found on the text website, labeled Revenue Passenger-Miles.

Year Month Revenue Passenger-Miles 2006 Jan 43.1652 2006 Feb 44.0447

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2010 Sep 43.7704 SOURCE: Bureau ofTransportation Statistics.

a. Plot the above series and comment on its trend and seasonal variations.

b. Compute seasonal indices and use them to seasonally adjust the series.

c. Fit the appropriate trend model to the seasonally adjusted series.

d. Use decomposition analysis to make monthly forecasts for the last three months of 2010.