The Figure Shows the Unregulated Market for a Pesticide, Where

Multiple Choice

The figure shows the unregulated market for a pesticide, where S is the supply curve and D is the demand curve. The demand curve is the same as the MSB curve. When factories produce the pesticide, they also create waste, which they dump into a lake on the outskirts of the town. The marginal external cost of the dumped waste is equal to the marginal private cost of producing the pesticide.
-In the figure above, if the output is 180 tons per month, what is the marginal social cost of producing the pesticide?

A) $60
B) $30
C) $40
D) $50