An airline sells all the tickets for a certain route at the same price. If it charges 200 dollars per ticket it sells 10,000 tickets. For every 5 dollars the ticket price is reduced, an extra thousand tickets are sold. Thus if the tickets are sold for 195 dollars each then 11,000 tickets
sell. It costs the airline 100 dollars to fly a person.
(a) Express the total profit P in terms of the number n of tickets sold.
(b) Express the total profit P in terms of the price p of one ticket.