Suppose that the number of hours per week of lost work due to illness in a certain automobile assembly plant is approximately normally distributed, with a mean of 40 hours and a standard deviation of 15 hours. For a given week, selected at random, what is the probability that (this question is worth 3 marks):

1. The number of lost work hours will exceed 70 hours?
2. The number of lost work hours will be between 30 and 45 hours?
3. The number of lost work hours will be exactly 50 hours?