The benefits and costs of sulfur dioxide emissions are given by: Benefit of reducing emission: MB = 500 - 20A Costs of reducing emissions: MC = 200 + 5A where A is the quantity of emision reduced in millions of tons and the benefits and costs are given in dollars per ton. a. What is the socially efficient level of emissions abatement (reduction)? 0.5 b. What are the marginal benefits and marginal cost of abatement at the socially 0.5 efficient level of abatement