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 25 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).