Consider 4 processes, arriving at 0, 0, 2, 5, with total execution time of 10, 20, 30 and 40 units, respectively. Each process spends the first 20% of execution time doing I/O, the next 70% of time doing computation, and the last 10% of time doing I/O again. The operating system uses a shortest remaining compute time first scheduling algorithm. For what percentage of time does the CPU remain idle?