How to solve the simulation work?

Question

Mathematics

We were asked to do the following task:
Simulate QS M/M/1/r with group service. Group service
assumes that at the end of the service of the previous group of requests, a
group of requests from the accumulator arrives for service at once, the size of which is
drawn randomly from the interval (1;r). If the current number of requests in the accumulator
is less than the size of the group, then all requests from the accumulator are received for servicing. If the
drive is empty at the end of servicing a group of requests, then the device resumes
servicing at the moment the first request arrives, i.e. in this case, the group size is 1.
All model parameters must be specified using stored values. Numeric
come up with the values ​​of the parameters yourself, but at the same time choose them in such
a way that the device load is equal to a number from the interval (0.8; 0.9). Construct the EGF
of the residence time of requests in the system.
You need to solve it in the GPSS World program, the very essence of the problem is approximately clear, but I don’t understand how to work in GPSS at all.
Tell me, please, either where they explain how to work with the program, or just help me decide.

Answer 1

https://habr.com/ru/post/192044/
https://habr.com/ru/post/488608/