A small private ambulance service in Kentucky has determined that the time between emergency calls is exponentially distributed with a mean of 41 minutes.

When a unit goes on call, it is out of service for 60 minutes. If a unit is busy when an emergency call is received, the call is immediately routed to another service. The company is considering buying a second ambulance. However, before doing so, the owners are interested in determining the probability that a call will come in before the ambulance is back in service.

Without knowing the costs involved in this situation, does this probability tend to support the need for a second ambulance? Discuss.