A Post Office Has a Single Line for Customers Waiting

Multiple Choice

A post office has a single line for customers waiting for the next available postal clerk.There are two postal clerks who work at the same rate.The arrival rate of customers follows a Poisson distribution,while the service time follows an exponential distribution.What type of queuing model applies here?

A) M/M/1
B) M/M/2
C) M/D/2
D) M/D/1
E) M/G/1