(1.5 points) Suppose that the demand for travel along a particular road is given by V=25-P, where V is the number of trips (traffic volume) and P is the price per trip. Suppose further that the private cost of travel equals (7+V/2), and the marginal external cost of travel due to congestion equals V/2.

a. Solve for the equilibrium and optimum levels of traffic volume.

b. Find the congestion toll that will induce drivers to take the optimum number of trips.