need this asap, definitely give a positive view

A city bus system carries 4000 passengers a day throughout a large city. The cost to ride the bus is $1.50 per person. The owner realizes that 100 fewer people would ride the bus for each $0.25 increase in fare, and 100 more people would ride for each $0.25 decrease in fare. If the capacity of the bus system is 5000 passengers, what should the bus system charge to produce the largest possible revenue