The waiting line at a popular bakery shop can be quite long. Suppose that the waiting time in minutes has probability density function fx (x) = {(0.1) e-(0.1)x 0, 0 otherwise Determine the following: a. F(x). b. Probability that a customer waits more than 20 minutes. c. Probability that a customer waits more than 20 minutes given that s/he waits at least 4 minutes.