4.2 Why is there waiting in an infinite-source queuing system? multiple-phase processing slow service variability in arrival and service rates low utilization poor scheduling of servers Solution The population or source in a queuing theory is divided into two parts including finite and infinite population. In infinite source queuing system, the number of customers in the system has no effect on the arrival pattern of customers. Besides it also experiences huge variability in the arrival rate of customers as well as the service rates. Due to this reason there is waiting in infinite-source queuing system. Hence, the correct option is variability in arrival and service rates..