DiscountAir is a service where frequent flyers pay a yearly flat rate and are guaranteed a seat on flights between any two locations. To offer this service, DiscountAir prepurchases daily seats between every pair of major cities. A route, which has been growing in popularity, is between Phoenix and Dallas. DiscountAir is seeking your advice on how many seats to prepurchase between these two cities so that they can earn the HIGHEST AVERAGE daily profit