A study of the demand for air travel in Australia found that the demand for discount air travel from Sydney to Melbourne (in revenue passenger kilometre per capita, the product of the number of passengers travelling on a route and the distance of the route, divided by the populations of the host cities) depends on the airfare according to the equation
$$q=55.2-0.022 p$$
Source: International Journal of Transport Economics.
a. Find the elasticity when the price is $\$ 166.10$ , the average dis- count airfare deflated by the consumer price index to $1989-1990$ prices, according to the authors of the study.
b. Is the demand for airfare elastic or inelastic at this price?
c. Find the price that maximizes revenue.