A dental clinic at which only one dentist works is open only two days a week. During those two days, patients is arriving at the rate of three per hour. The doctor serves patients at the rate of one every 10 minutes. a) What is the probability that the clinic is empty (except for the dentist)? b) What is the probability that there are five or more patients in the system? c) What is the probability that there are fewer than three patients in the system? d) What is the probability that there are six patients in the system?