The numbers of commercial airline boardings on domestic flights are shown in Table 53 for various years.

Let n be the number (in millions) of commercial airline boardings on domestic flights for the year that is t years since 1990.
a. Construct a scatterplot.
b. Identify the outlier. Explain how the terrorist attacks in 2001 are related to the outlier.
c. Determine whether the outlier is an influential point.
d. Find the linear regression equation after the data point for 2001 is removed. Use the equation to estimate the number of boardings in 2001. Estimate how much the number of boardings were affected due to the terrorist attacks.
e. By making the following assumptions, estimate the amount of money airlines lost in 2001.
€¢ All trips were round trips.
€¢ The average number of boardings for a round trip was four (two flights out, two back).
€¢ The average round-trip fare was $340.

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Table 53 Numbers of Commercial Airline Boardings on Domestic Flights Number of Boardings (millions) Year 1991 1993 1998 1997 1999 2001 452 487 547 599 635 622