During this 25 second interval, the Intern's phone appears busy. The service time for calls reaching the Intern have a triangular distribution ranging from 2 to 5 minutes, with the majority taking 4 minutes. Callers hate voice mail. Voice mail gives callers an opportunity to transfer their call to the Intern. The service time of calls in voice mail is not relevant since the phone becomes free as soon as the transfer takes place and the voice mail system can handle a large number of calls simultaneously.
Customers also dislike having to call repeatedly.
Assume the time between calls is a triangular distribution ranging from 10 minutes to 10 hours, with most calling back in an hour. Currently service time is 14 minutes. Management also wants the model run assuming service times of 14 and 18 minutes. They want both absolute numbers and percentages. Management is also considering a new telephone system.