Both Wisconsin and Illinois border Lake Michigan. The lake is becoming polluted and both states are deciding whether or not to clean it. If Wisconsin decides to clean the lake it will cost 1200 and generate social benefits of 1500 – however, Wisconsin will receive only 1100 of those social benefits while neighbor Illinois will receive the other 400. If Illinois cleans the lake, it will cost them 700 and generate social benefits of 900 – however, Illinois will receive only 600 of those benefits, Wisconsin will receive the remaining 300. If a state does not clean the lake, it experiences a cost of $0. If both states clean the lake, the payoffs will be

A. Wisconsin gains 100, Illinois gains 200
B. Wisconsin gains 200, Illinois gains 300
C. Wisconsin gains 200, Illinois loses 100
D. Wisconsin gains 100, Illinois loses 100

Assuming that one state cleaning the lake does not interfere with the costs and social benefits of the other state (events are independent), Wisconsin will incur 1,200 in costs and receive 1,100 in benefits from its own cleaning and 300 from Illinois' cleaning. Illinois will incur costs of 900 and receive 600 in benefits from its own cleaning and 400 from Wisconsin's cleaning.

The payoff for each state is:

[tex]W = -1,200+1,100+300\\W=200\\I=-700+600+400\\I=300[/tex]

Therefore, Wisconsin gains 200, Illinois gains 300.