By making furniture at home in the evening, however, individual A creates noise with power tools and other equipment, which drives his or her neighbor to eat out or to go to a movie or a bar. Suppose that the private marginal cost imposed on individual B from each additional hour of evening work by individual A is given the MPCb curve. The marginal social cost of evening work by individual A is then given by the MSC curve, which is the vertical summation of the MPCa and MPCb curves. At the best number of 4 hours of evening work by individual A, the MSC of $10 (point c) exceeds the MPBa of $6 (point Ea). It is, therefore, economically inefficient from society ‘ s point of view for individual A to work 4 hours. From society’ s point of view, individual A should work only 3 hours per evening, which is given by point Es, at which MSC = MPBa =$8.