The Controller of XYZ Company is concerned about the how much the companys costs have risen over the past few months. Since the majority of the companys costs are mixed, it is hard to tell if the increasing costs are due to variable costs or fixed costs. The controller asks that you the cost manager to research the different ways to separate mixed costs and then to present a report showing the advantages and disadvantages of each method. He would also like you to make a recommendation as to which method should be used.