Suppose that rainfall duration follows an exponential distribution with mean value 2.725 hours.
a. What is the probability that the duration of a particular rainfall event is at least 2 hours? At most 3 hours? Between 2 and 3 hours? (.4800, .6674, .1474)
b. What is the probability that rainfall duration exceeds the mean value by more than 2 standard deviations? (.0498)
c. What is the probability that it is less than the mean value by more than one standard deviation? (0)
My try: I got part a) and I am getting 0.668 for b) but answer should be 0.0498 and same for par c). I got 0.236 for part c but it should be 0 according the solution in the back.
Can someone help me with part b and c.