Within a healthcare setting, list and explain the four different mechanisms that private insurers have in place to limit the use of insured services. Are these mechanisms necessary? Explain the nature of the market failure they intend to mitigate.

(NOTE: I have one final assignment due tomorrow, and this is one of the seven questions. I've been completing my weekly readings. However, I'm having difficulty answering this question as the textbook doesn't elaborate in depth on this topic. So, I can use some help with an explanation to guide me in the right track. The answer should be based in a U.S. healthcare market). THANK YOU!