The Madison Fire Department’s files reveal that an average of six firefighters a year suffers heart attacks while on duty. The personnel office is concerned about this because it must budget funds for disabilities. There are some concerns that the physical condition of firefighters is getting worse. This year, nine firefighters suffered heart attacks. What is the probability that an event of this severity will occur? Given past history, what is the probability that no heart attacks will occur? Exactly one? Exactly two? Three or fewer?