2. An online retailer has determined that the average time for credit card transactions to be electronically approved is 1.6 seconds. (a) Use an exponential density function to nd the probability that a customer waits less than a second for credit card approval. (Hint: Exponential probability density functions are of the form f (:23) = le'E/'L when a: 2 0, and zero p. otherwise.) (b) Find the probability that a customer waits more than 3 seconds. Your answer should be less than 0.2. (c) What is the minimum approval time for the slowest 5% of transactions? Your answer should be close to 5 seconds