Following Questions Are Based on the Following Information

Multiple Choice

Following Questions are based on the following information.
In a small city located on a lake,the raw sewage of the city is dumped directly into the lakE.This has been a source of distress for citizens who like to swim,fish,and water ski.A study has been instituted to determine what value the citizens place on pollution control,and the results are listed in the following tablE.Costs of pollution control are also listed.

-The marginal social cost of the fourth unit of pollution control is

A) Zero
B) $30,000
C) $90,000
D) $100,000
E) $120,000