Originally Posted by

**engineer22** **1)** The length of time, Y, that a customer spends in line at a bank teller's window before being served is described by the exponential pdf:

f(y) = 0.2e-0.2y, y ³ 0.

a) What is the probability that a customer will wait for more than 10 minutes?

I used 1 - P( Y £ 10 ) = 1 - 0.2e-0.2y = **0.9729**

b) Suppose the customer will leave if the wait is more than 10 minutes. Assume that the customer goes to the bank 3 times next month. Let the random variable X be the number of times the customer leaves without being served. Find P(X=1).

This I'm not sure how to do. Any hints?