8 The New York Times (17 February 1996) reported that subway use declined after a fare increase: 'There were nearly four million fewer riders in December 1995, the first full month after the price of a token increased 25 cents to $1.50, than in the previous December, a 4.3 per cent decline.'

a Use these data to estimate the price elasticity of demand for subway rides.

b According to your estimate, what happens to the revenue when the fare rises?

c Why might your estimate of the elasticity be unreliable?