A university offers a walking escort service to increase security around campus. The system consists of specially trained uniformed professional security officers that accompany students from one campus location to another. The ser- vice is operated 24 hours a day, seven days a week. Students request a walking escort by phone. Requests for escorts are received, on average, every 5 minutes with a coefficient of variation of 1. After receiving a request, the dispatcher contacts an available escort (via a Variability and Its Impact on Process Performance: Waiting Time Problems 181 mobile phone), who immediately proceeds to pick up the student and walk her/him to her/ his destination. If there are no escorts available (that is, they are all either walking a stu- dent to her/his destination or walking to pick up a student), the dispatcher puts the request in a queue until an escort becomes available. An escort takes, on average, 25 minutes for picking up a student and taking her/him to her/his desired location (the coefficient of varia- tion of this time is also 1). Currently, the university has 8 security officers who work as walking escorts
a. How many security officers are, on average, available to satisfy a new request?
b. How much time does it take on average from the moment a student calls for an escort to the moment the student arrives at her/his destination?