Question

The length of long distance phone calls, measured in minutes, is known to have an exponential...

The length of long distance phone calls, measured in minutes, is known to have an exponential distribution with E(X)=2.

a) Find the probability that a phone call lasts less than 9 minutes

b) Find the probability that a phone call lass between 7 and 9 minutes

c) If 3 phone calls are made one after another, on average, what would you expect the total to be?

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