The Flight for Life emergency helicopter service is available for medical emergencies occurring from 15 to 90 miles from the hospital. Emergencies that occur closer to the hospital can be handled effectively by ambulance service. A long-term study of the service shows that the response time from receipt of the dispatch call to arrival at the scene of the emergency is normally distributed, with a mean of 42 minutes and a standard deviation of 8 minutes. For a randomly received call, what is the probability that the response time will be
(a) Between 30 and 45 minutes?
(b) Less than 30 minutes?
(c) Longer than 60 minutes?