a server operates with 80% utilization. the coefficient of a server operates with 80% utilization. the coefficient of variation for the service process is 0.5 and the coefficient of variation of the arrival process is 1. the average processing time is 3 minutes. what is the average time a customer spends in the system according to the single-server queue model? for the service process is 0.5 and the coefficient of variation of the arrival process is 1. the average processing time is 3 minutes. what is the average time a customer spends in the system according to the single-server queue model?