Ans is B
Since order of cpu and i/o is not mentioned in the question .so we shall arrange the process in the following order:
Process Arr-Time CPU Time I/O Time CPU Time
P1 0 5 5 5
P2 0 5 5 5
Now the Gantt chart:
0 5 P1 I/0 10 P2 I/O 1 5 20
So it will take Total time=20 min