The answer is:
advantages and disadvantages of making a decision
a way to find the choice that gives you the most gains from a decision
a rational approach to decision making
Cost benefit analysis is a form of analysis that is made to find out the strength and weaknesses of all of our options. During cost benefit analysis, finding out the advantages and disadvantages of each options we can identify the gains and expenses that would occurs from each options.
All of this information would help us making the most rational approach that make us know the best possible options/decisions for us.