Customers arrive at a two$-$server system according to a Poisson process with rate $\backslash$lambda $=10$ per hour. An arrival finding server $1$ free will begin his service with him. An arrival finding server $1$ busy, server $2$ free will join server $2.$ An arrival finding both servers busy goes away. Once a customer is served by either server, he departs the system. The service times at both servers are exponential random variables. Assume that the service rate ofthe first server is $6$ per hour and the service rate of the second sever is p $4$ per hour