adding and vertically, we derive society’s marginal benefit
curve, The marginal cost of providing the public good is shown
by MC. The allocatively efficient level of the public good is where the
marginal cost to society is just equal to the marginal benefit to society. At
, the marginal benefit to society is the sum of the individual
marginal benefits to Andrew (a) and Brenda (b).
MBA MBB
MBA+B.
Q∗,Q∗ a+b,