A tax consultant wonders whether he should be more selective about the class of clients he serves so as to maximize his income. He usually deals with four categories of clients: the very rich, rich, upper middle class, and middle class. He has records of each and every client served, the taxes paid by them, and how much he has charged them. Since many particulars in respect of the clients vary (number of dependants, business deductibles, etc.), irrespective of the category they belong to, he would like an appropriate analysis to be done to see which among the four categories of clientele he should choose to continue to serve in the future. What kind of analysis should be done in this case and why?