17. a certain university has a great deal of turnover among its deans of astrology. they quit or are fired, unpredictably, on average after 2.5 years. then the president immediately appoints a new dean. a) what is the probability the current dean will quit or be fired within the next 3.0 years? b) what are the mean and standard deviation of the number of deans who will quit or be fired within the next 8.0 years?