1.Process makes the operating system can do different things in the same time and they would not influent each other.
2.
a)
FCFS:
P1 P2 P3 P4 P5
0 10 11 13 14 19
SJF:
P2 P4 P3 P5 P1
0 1 2 4 9 19
Non-preemptive:
P2 P5 P1 P3 P4
0 1 6