Question 4 - Driving Taxes Consider driving as a market activity. The Private Marginal Cost of adding 1 driver to the roads is: PM0212+T212+Q This is a model where travel time is given by T and this is equal to Q: is the total number of drivers on the road. To derive the external cost caused by the ch driver, use the formula 130(62): M x (Q 1) This is the increase in travel time, multiplied by the number of drivers already on the road. (a) Find the equation for the Social Marginal Cost {8M0} as a function of Q The marginal benet of adding 1 more driver is given by PM B : SM B : 36 3Q. (b) What is the free-market equilibrium number of drivers Q*? (c) What is the socially optimal number of drivers QB? (d) What road usage charge (tax) would lead to Q3 drivers on the road