Suppose that prior to the land restrictions of 1984, the market for land disposal was modeled as follows:

D = MPB = 80 − 2L

S = MPC = 20 + 2L,

where L is thousands of tons of landfilled hazardous waste, and the dollar values are per ton.

When the 1984 restrictions decreased the supply of land disposal services, assume that the marginal private costs (MPC) of production decreased to MPC′ = 32 + 2L. 

a. Based on this model, quantify the price increase in land disposal accomplished by the restrictions and the associated decline in landfilling.

b. Graphically show the qualitative effect on total external costs in the land disposal market.