Our classroom (MNT 203) is lit partially by fluorescent tubes, each of which fails, on average, after 4000 hours of operation. Since it is costly to have a technician in place to replace tubes whenever they fail, the management decided to check them for replacement after 3000 hours. Assuming that we have 300 fluorescent tubes in MNT 203: a. What is the probability that the first tube fails before 1000 hours? b. On average, how many failed tubes will be replaced on 3000 hours replacement check?