A band performs a concert in a 400-seat auditorium. Local businesses buy the tickets in blocks of 10. Tickets go on sale to businesses for 4 hours only the day before the concert. The process of placing orders for tickets is Poisson with a mean 10 calls per hour. Any blocks of tickets remaining after the box office is closed are sold at discount as "rush tickets" 1 hour before the concert starts.
A) What is the probability that it will be possible to buy a rush ticket
B) What is the average number of rush tickets available?