A delicatessen located in the heart of the business district of a large city serves a variety of customers. The delicatessen is open 24 hours a day every day of the week. In an effort to speed up take-out orders, the deli accepts orders by fax. If, on the average, 20 orders are received by fax every two hours throughout the day, find the
a. Probability that a faxed order will arrive within the next 9 minutes
b. Probability that the time between two faxed orders will be between 3 and 6 minutes
c. Probability that 12 or more minutes will elapse between faxed orders