Benefits of abating emission: MB=500-20A Cost of abating emission: MC=200+5A What are the marginal benefit and marginal cost of abatement at socially...

Benefits of abating emission: MB=500-20A

Cost of abating emission: MC=200+5A

What are the marginal benefit and marginal cost of abatement at socially efficient level of abatement? What is the net social benefit at the efficient level?

How could we get 1800?

Thanks