A study finds that the noise from airplanes is harmful; hence, the government imposes a $25 tax on the sale of every airplane. This amount accurately accounts for the external cost of the noise pollution. Before the corrective tax, airplane tickets regularly sold for $190. After the tax is in place, the market price for airplane tickets rises to $200.A study finds that the noise from airplanes is harmful; hence, the government imposes a $25 tax on the sale of every airplane. This amount accurately accounts for the external cost of the noise pollution. Before the corrective tax, airplane tickets regularly sold for $190. After the tax is in place, the market price for airplane tickets rises to $200.a. Because of the tax, the number of airplane tickets sold will decrease . b. The socially optimal price of airplane tickets is $ c. The private market price is $ d. A firm selling airplane tickets receives $ after it pays the tax.

Financial markets and channel to . they also channel money from individuals who want to for the future to those who need cash to spend today. a third function of financial markets is to allow individuals and businesses to adjust their risk. for example, , such as the vanguard index fund, and , such as spdr's or “spiders,” allow individuals to spread their risk across a large number of stocks. financial markets provide other mechanisms for sharing risks. for example, a wheat farmer and a baker may use the to reduce their exposure to wheat prices. financial markets and intermediaries allow investors to turn an investment into cash when needed. for example, the of public companies are because they are traded in huge volumes on the . are the main providers of payment services by offering checking accounts and electronic transfers. finally, financial markets provide information. for example, the of a company that is contemplating an issue of debt can look at the yields on existing to gauge how much interest the company will need to pay.