Suppose That an Office Has One Secretary Who Can Put

Multiple Choice

Suppose that an office has one secretary who can put up to two callers on hold while speaking to a third caller.(If two callers are on hold, additional callers will get a busy signal and will not
Call back.) If the arrival rate of calls follows a Poisson
Distribution with a mean rate of 20 per hour and the average length
Of a telephone conversation is 2 minutes, the average number of
Callers who will be on hold is approximately:

A) 2.0.
B) 1.3333
C) 1.0154.
D) .4308.