Better Battery Has Been in the Battery Renewal Business for Four

Better Battery has been in the battery renewal business for four years.It rents a building but owns all of its equipment.All employees are paid a fixed salary except for the busy season (April - June), when temporary help is hired by the hour.Utilities and other operating charges remain fairly constant during each month, except those in the busy season.Selling prices per battery average $100, except during the busy season.Because a large number of customers buy batteries prior to winter, discounts run above average during the busy season.A 15 percent discount is given when two batteries are purchased at one time.During the busy months selling prices per battery average $90.The president of Better Battery is somewhat displeased with the company's management accounting system because the cost behaviour pattern displayed by the monthly break-even charts are inconsistent; the busy month's charts are different from the other months of the year.The president is never sure if the company has a satisfactory margin of safety or if it is just above the break-even point.Required:
a.What is wrong with the accountant's computations?
b.How can the information be presented in a better format for the president?