1.000: Customer 0 arrives
1.000: Customer 0 service begin (by Counter 0)
1.100: Customer 1 arrives
1.100: Customer 1 service begin (by Counter 1)
2.000: Customer 0 service done (by Counter 0)
2.000: Customer 0 departed
2.100: Customer 1 service done (by Counter 1)
2.100: Customer 1 departed
2.200: Customer 2 arrives
2.200: Customer 2 service begin (by Counter 0)
2.300: Customer 3 arrives
2.300: Customer 3 service begin (by Counter 1)
3.200: Customer 2 service done (by Counter 0)
3.200: Customer 2 departed
3.300: Customer 3 service done (by Counter 1)
3.300: Customer 3 departed
