After you have studied Economics in the News on pp. 386–387, answer the following questions:a. What is the source of revenue for constructing and maintaining the transportation infrastructure?b. Why has that revenue source not grown fast enough to deliver an efficient scale of infra­structure provision?c. What other revenue sources can you suggest that could provide a solution to underprovision?d. How would you expect population growth to influence the marginal social benefit of high­ways and bridges?e. Illustrate your answer to (d) by drawing a version of the figure on p. 385 that shows the effect of an increase in population.