The difference between the unitary, confederal, and federal systems of power-sharing.

Explain the difference between the unitary, confederal, and federal systems of power-sharing. Give examples of countries practicing each type of the power-sharing system. What type of power-sharing system does the United States use today?
What was the very first type of grants-in-aid provided by the federal government to states? Compare and contrast categorical grants and block grants. What problems are associated with the categorical grants? Why did the federal government introduce block grants? Why did block grants fail to result in considerable freedom and lighter tax burden? Give examples for each type of grants-in-aid.