$2)$ A two server system and infinite queue.

The interarrival time follows the exponential distribution with an arrival rate equal to $4$

parts$/$hr$.$ The average service time of a server is $12$ minutes. Service time also follows

the exponential distribution.

a$0=4$ parts$/$hr

al $=4$ parts$/$hr

a$2=4$ parts$/$hr

$0$

$1$

$2$

$3$

d$1=5$ parts$/$hr

d$2=10$ parts$/$hr d$3=10$ parts$/$hr