The present paper deals with the study of mathematical and graphical study of mean queue length of the system. The Queuing system has four servers for the service of customers. A customer, after getting service from first server goes to second or third or fourth server for service depending upon the need of service. She/he is allowed to revisit but not more than once. The arrival and service pattern are assumed to follow the Poisson process. The Mean Queue Length of the system has been calculated by solving the steady state equations by using the generating function technique.

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Keywords: Feedback, Queuing System, Poisson Process, Four Server, Mean Queue Length.