Final answer:
In economics, the production of steel has negative externalities like pollution that are not reflected in its market price, leading to a higher market quantity than the socially optimal amount. A price increase in steel leads to a decrease in the quantity supplied by car manufacturers. The government can intervene to make producers internalize external costs, leading to an efficient equilibrium.
Step-by-step explanation:
The question involves understanding the externalities and market equilibrium in steel production - a topic under economics. Negative externalities of steel production may include pollution, health issues related to pollution, and depletion of natural resources. These costs are not reflected in the market price of steel, leading to what economists call market failure. The market equilibrium does not account for these social costs, and thus, the market quantity is higher than the socially optimal quantity.
When the price of steel rises, car manufacturers will supply a lower quantity of cars, which can be represented by a leftward shift in the supply curve from So to S₁. At the price of $20,000, the quantity supplied decreases from 18 million to 16.5 million. To correct for the externalities, the government can implement policies such as taxes or regulations, which force manufacturers to internalize the full costs of production, shifting the supply curve leftward and reducing the quantity produced to a socially efficient equilibrium.