What is Round Robin's behavior when a process comes at the same time that the old process is swapped out?
P1 arrives at time 0 and needs 3 seconds to process. 

P2 arrived at time 2 and needs 1 second to process.

Processing

P1 arrives first and will process 2 second because time quantum is 2s. 1s left. 

After processing P1 (2 seconds later), P2 will arrive.

It will completely process it and then return back to P1. 

1 second later both processes are processed.