Attempts Keep the Highest / 1 9 . Efficiency in the presence of externalities Public wifi hotspots grant many external benefits on society: more equitable access to the internet, increased educational opportunities, Therefore, the market equilibrium quantity of public wifi hotspots does not equal the socially optimal quantity. The following graph plots for public wifi hotspots (their private value), the supply of public wifi hotspots (the private cost of producing them), and the social value hotspots, including both the private value and external benefits. Use the black point (plus symbol) to indicate the market equilibrium quantity. Next, use the purple point (diamond symbol) to indicate optimal quantity. Supply (Private Cost) Market Equilibrium Socially Optimal Level PRICE OF PUBLIC WIFI HOTSPOTS Social Value Demand (Private Value) QUANTITY OF PUBLIC WIFI HOTSPOTS10 . Understanding different policy options to correct for negativeexternalities Carbon dioxide emissions have been linked to degradation of air quality. The following table lists some potential regulations targeting the amount of airborne carbon dioxide. For each policy listed, identify whether it is a command-and-control policy (regulation), tradable permit system, corrective subsidy, or corrective tax. Tradable Command-and- Permit Corrective Corrective Public Policy Control Policy System Subsidy Tax Trees take carbon dioxide out of the air and convert it to oxygen, so the government funds a tree-planting initiative by offering $270 to any citizen O O O O who plants a tree. The government charges factories $270 for every ton of carbon dioxide O O O O they emit. The government orders every factory to adopt a new technology, which O O O O reduces carbon-dioxide emissions into the atmosphere. The government limits total carbon-dioxide emissions by all factories to 240,000 tons per year. Each individual factory is given the right to emit O O O O 220 tons of carbon dioxide, and factories may buy and sell these rights in a marketplace