Suppose that the increase in the fee from $8 to $16 reduces travel time in the central city from 30 minutes down to 20 minutes. what is the percentage change in the total cost of driving in central london?

With regards to the change in total cost driving to London, the price doubled from $8 to $16. So the total change in cost was $8 or 50% price change. However, though there is an increase in price, the travel time goes down, which is optimal in heavy traffic.

If your choices are the following:

a) $20

b) $12

c) $10

d) $8

e) $5

Then the answer is letter e. 16-8 = 8 so this is the difference between the 10 minutes. So this means 8 is the best answer.