The data in the table show the marginal costs and marginal benefits to a city for five different levels of pollution control.Quantity of Pollution AbatementMarginal CostMarginal Benefit900 tons$400,000$100,000800 tons300,000150,000700 tons200,000200,000600 tons100,000250,000500 tons50,000300,000Refer to the above table. What would cause the optimal level of pollution abatement to be 600 tons?

A. An increase in marginal benefits by $200,000 at each level.
B. An increase in marginal costs by $150,000 at each level.
C. A decrease in marginal costs by $150,000 at each level.
D. A decrease in marginal benefits by $100,000 at each level.

answer:

B. An increase in marginal costs by $150,000 at each level.