The manager of a fast-food restaurant determines that the average time that her customers wait for service is 1.5 minutes. (a) Find the probability that a customer has to wait more than 5 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 2% of her customers. What number of minutes should the advertisement use