Please solve for A and B

A local club is arranging a charter flight to Hawaii. The cost of the trip is $573 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 a. The number of passengers that will maximize the revenue received from the flight is (Round to the nearest integer as needed.) b. The maximum revenue is $