7.3 Exercise 24

Twenty “identical” units are put into operation. They fail independently. The times to failure (in hours) form an iid class, exponential (0.0002). This means the “expected” life is 5000 hours. Determine the probabilities that at least k, for $k = 5 , 8 , 10 , 12 , 15$, will survive for 5000 hours.