It's a question in the book named simulation modeling and arena Author Manuel D.Rossetti

EXERCISES 385 1.11 In a four-server facility, the number of busy servers changes with time as shown below Compute the following measures of performance over a period of 25 time units (a) Average number of busy servers (b) Average busy time per server. (c) Average idle time per server (d) The utilization of the servers. Number of busy servers 3 10 15 20 25 Time T