The manager of a fast-food restaurant determines that the average time that her customers wait for service is 2.5 minutes. This process can be described using an exponential probability density function with a mean of 2.5. a. Find the probability that a customer has to wait more than 4 minutes. (Round your answer to three decimal places.)
b. Find the probability that a customer is served within the first minute. (Round your answer to three decimal places.)
c. The manager wants to advertise that anybody who isn't served within a certain number of minutes gets a free hamburger. But she doesn't want to give away free hamburgers to more than 1% of her customers. What number of minutes should the advertisement use?