The length of time in minutes, Y, that a customer spends in line at a bank teller’s window before being served is described by the exponential pdf f(y) = 0.2exp(-0.2y) y>0.

a) What is the median (m) waiting time in minutes and seconds?

Is this 0.2 = 1/m thus m = 5?

b) What is the probability that a customer will wait more than 10 minutes? Answer correct to 3 decimal places.

Do I just replace y with 10 here? Thus -0.4

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

I'm not sure about this one at all.