A cafeteria serving line has a colfee urn from which customers serve themselves. Arrivals at the urn follow a Poisson distribution at the rate of 3.0 per minute. In serving themselves, customers take about 12 seconds, exponentlally distributed. a. How many customers would you expect to see, on average, at the coffee urn? (Do not round intermediate calculations. Round your answer to 2 decimal places.) b. How long would you expect it to take to get a cup of coffee? (Round your answer to 2 decimal places.) c. What percentage of time is the urn being used? (Do not round intermediate calculations. Round your answer to 1 decimal place.)