What are the four economic types of mergers? What’s the difference between a hostile and a friendly merger?

What five major “merger waves” have occurred in the United States?
What are some reasons for the current wave?

What are the four economic types of mergers?

What’s the difference between a hostile and a friendly merger?

Is there a need to regulate mergers? Explain.
Do the states play a role in merger regulation, or is it all done at the
national level? Explain.