What is the role of the U.S. government, in terms of dealing with the problem of income inequalities? What are the arguments, for and against,

What is the role of the U.S. government, in terms of dealing with the problem of income inequalities? What are the arguments, for and against, government involvement in this area?
Why do nations trade? What is meant by the concept of "Comparative Advantage"? Could a nation be better off economically, if it practiced an isolation policy?
The United States has had a significant trade imbalance for several years. What are the problems associated with having a negative trade balance? What can be done to correct the imbalance?
How are exchange rates determined? What is the significance of currency devaluations to the home country? To other countries?