ABC corp conducted a study of service times at the drive-up window of fast-food restaurants. The average time between placing an order and receiving the order at restaurant is 2.45 minutes. Assume that the waiting time follows exponential distribution. a. What is the probability that service time is less than 1.5 minutes?
Setup:
$$\lambda = 1/2.45$$
$$P(X < t=1.5) = {1-e^{-\lambda t}} = 0.46$$
is it correct?
b. A customer has been waiting for 3 minutes after placing an order, what is the expected value of remaining waiting time?
Question : how to work for remaining waiting time?