1.000: Customer 0 arrives
1.000: Customer 0 service begin (by Counter 0)
2.000: Customer 0 service done (by Counter 0)
2.000: Customer 0 departed
3.000: Customer 1 arrives
3.000: Customer 1 service begin (by Counter 0)
4.000: Customer 1 service done (by Counter 0)
4.000: Customer 1 departed
5.000: Customer 2 arrives
5.000: Customer 2 service begin (by Counter 0)
6.000: Customer 2 service done (by Counter 0)
6.000: Customer 2 departed
