Consider a queueing system with $$ servers. The incoming customers belong to one of two classes: $1$ and $2.$ Class $2$ customers are allowed to enter the system if and only if there is a free server immediately available upon their arrival, otherwise, they are turned away. Class $1$ customers always enter the system and wait in an infinite capacity waiting room for service if necessary. Assume that the interarrival time for class $$ customers is $(),=1,2.$ The service time is $()$ for both classes. Define the state as the number of customers in the system and give a queueing model for this system.