With higher fuel costs, airlines raised their average fare from 75 to $1.25 per passenger mile and

Question:

With higher fuel costs, airlines raised their average fare from 75¢ to $1.25 per passenger mile and the number of passenger miles decreased from 2.5 million a day to 1.5 million a day.
a. What is the price elasticity of demand for air travel over this price range?
b. Describe the demand for air travel.