Marginal Analysis:. Doug Ross is a regional sales representative for Specialty Books, Inc., and sellstextbooks to universities in Midwestern states. Ross’ goal is to maximize total monthly commissionincome, which is figured at 10% of gross sales. In reviewing monthly experience over the past year, Rossfound the following relations between days spent in each state and monthly sales generated:If administrative duties limit Ross to only 15 selling days per month, how should he spend them?I know that the answer will be somehow related to the amount of marginal sales per day, but dont know how exactly to determine the allocation.Thanks