Answer Happy

Bill Youngdahl has been collecting data at the TU student grill.
He has found​ that, between​ 5:00 P.M. and​7:00 P.M., students
arrive at the grill at a rate of 20 per hour​ (Poisson distributed)
and service time takes an average of 2.0 minutes​ (negative
exponential​ distribution). There is only 1​ server, who can work
on only 1 order at a time.
​a) The average number in the line​ =? customers ​(round your
response to two decimal​ places).
​b) The average time in the system​ =? minutes ​(round your
response to one decimal​ place).
​c) Suppose that a second server can be added to team up with
the first​ (and, in​ effect, act as one faster​server). This would
reduce the average service time to 90 seconds. The average time in
the system​ = ? minutes ​(round your response to two decimal​
places). ​
d) Suppose a second server is added and the 2 servers
act​independently, with each taking an average of 2.0 minutes. If a
second server is​ added, the average time a customer spends in the
system​ =? minutes ​(round your response to two
decimal​places).