question 3 please. 3. Suppose that the lapse of time between two successive accidents in a paper mill is exponentially distributed with a mean of 15 days. Find the probability that the time between two successive accidents at that mill is more than 20 days. 4. Let a random variable X be distributed exponentially with mean equal to 10. Find the m.g.f. of the random variable Y=4+3X. Then, use this m.g.f. to find the mean.