4. Suppose the marginal benefit (MB) and marginal cost (MC) curves for emitting particulate matter are given by the following schedules, where E is the quantity of emissions per period. The marginal benefits and costs are measured at the quantities of emissions shown.

E/period MB MC 0 $230 $0 200 190 10 400 150 30 600 110 50 800 70 70 1,000 30 90