Consider three processes P1, P2 and P3 with arrival time of 0,1 and 2 time units respectively, and  total execution time of 20, 30 and 40 units respectively. Each process spends the first 30% of execution time doing I/O, then next 60% doing CPU and remaining 10% time doing I/O again. The operating uses a First come first serve scheduling algorithm and schedules a new process either when the running process gets blocked on I/O or when the running process finishes its compute burst. For what percentage of time does the CPU remain idle?

NOTE:
Ideal time at the start and at the end is counted.