GATE 2005 CPU scheduling PYQ

GATE 2005

We wish to schedule three processes P1, P2 and  P3 on a uniprocessor system. The priorities, CPU  time requirements and arrival times of the  processes are as shown below. 

Process

Priority

CPU Time Required

Arrival Time

(hh : mm : ss)

P1

10

(highest)

20 sec

00:00:05

P2

9

10 sec

00:00:03

P3

8

(lowest)

15 sec

00:00:00

We have a choice of preemptive or nonpreemptive scheduling. In preemptive scheduling,  a late-arriving higher priority process can  preempt a currently running process with lower  priority. In non-preemptive scheduling, a latearriving higher priority process must wait for the  currently executing process to complete before it  can be scheduled on the processor. What are the  turnaround times (time from arrival tili  completion) of P2 using preemptive and nonpreemptive scheduling respectively? 
(a) 30 sec, 30 sec 
(b) 30 sec, 10 sec  
(c) 42 sec, 42 sec 
(d) 30 sec, 42 sec