Consider the market for steel. Suppose that a steel manufacturing plant dumps toxic waste into a nearby river, creating a negative externality for those living downstream from the plant. Producing an additional ton of steel imposes a constant external cost of $490 per ton. The following graph shows the demand (private value) curve and the supply (private cost) curve for steel. Use the purple points (diamond symbol) to plot the social cost curve when the external cost is $490 per ton. 1400 1260 O Social Cost 1120 980 O Supply 840 (Private Cost) 700 PRICE (Dollars per ton of steel) 560 420 280 Demand 140 Private Value) 2 5 6 QUANTITY (Tons of steel) The market equilibrium quantity is _tons of steel, but the socially optimal quantity of steel production is tons. To create an incentive for the firm to produce the socially optimal quantity of steel, the government could impose a of $ per ton of steel