2.49 For the fleet described in Exercise 2.48,

a. Construct a simple tabulation in which the counts are according to the type of engine.

b. Construct a cross-tabulation describing the fleet, using type of engine and whether the vehicle has air conditioning as the categorization variables.

c. Construct a display showing the average mpg according to type of engine and whether the vehicle has air conditioning. Do the categorization variables seem to be related to mpg? If so, how?