A local club is arranging a charter flight to Hawaii. The cost of the trip is $ 551 each for 80 passengers, with a refund of $5 per passenger for...

A local club is arranging a charter flight to Hawaii. The cost of the trip is ​$551 each for 80 ​passengers, with a refund of​ $5 per passenger for each passenger in excess of 80.

a. Find the number of passengers that will maximize the revenue received from the flight.

b. Find the maximum revenue.