GATE Previous Year [closed]

Question

Consider three Processes P1 , P2, P3 arriving in the Ready Queue at time 0 in the order P1, P2, P3 Their service time requirements are 10, 20 & 30 units respectively. Each Process spends 20% of its Service time on I/O followed by 70% of its Service time on Computation at CPU and last 10% on I/O before completion.

Assuming Concurrent I/O and Scheduling Overhead to be 1 second. Calculate for FCFS Scheduling

(i) Average TAT of Processes

(2)% CPU idleness.