Why do economists measure the cost or money price of things when opportunity cost is what we actually are considering when we deciding whether or not to purchase?

How does federalism limit the power of government in the united states? a. it requires the national government to share power with state governments. b. it ensures that one state cannot make laws that affect all the other states. c. it requires the three branches of the national government to share powers. d. it allows the judicial branch to rule on laws that affect the entire country.

John lennon and paul mccartney belonged to this group

How did the spanish prove to be excellent allies in the war? give examples?