Suppose that Dexter and Amy live in a community that is trying to determine how much of the public good should be produced. Dexter's (inverse) demand curve is given by P = 20 - Q while Amy's (inverse) demand curve is given by P = 10 - 0.25Q. The marginal cost of producing the public good is constant at $2. What is the community's willingness to pay for the 24th unit of the public good?
a. $0
b. $2
c. $6
d. $15
e. None of the answers is correct.