Answer
*Cost benefit analysis of public goods: comparison between the costs and benefits of implementing public goods.
*It is important because the government needs to asses which goods the citizens value the most.
*it is hard because you cannot quantify benefit.
Work Step by Step
*Also it is important because governments need to know if benefit exceeds cost.
*It is hard because citizens won't tell the truth or won't participate to tell the truth, on how much benefit they got from a good provided to them.