The following graph shows the demand ( marginal private benefits) and supply (marginal private costs) curves for a good. The dashed drop lines on the graph reflect the market equilibrium price and quantity for this good. Suppose that a positive externality arises as a result of the production of this good. Adjust the following graph by shifting one of the curves to reflect the presence of the positive externality. O Supply Demand Supply PRICE AND COST Demand less greater The socially optimal output is than the market output