21. On a particular brand of disk drive, the time that it takes for the disk arm to pass over a single disk track without stopping is 500 nanoseconds. However, once the head reaches the track for which it has a service request; it needs 2 milliseconds to“settle”over the required track before it can start reading or writing. Based on these timings, compare the relative times required for FCFS, SSTF, and LOOK to carry out the schedule given below. You will need to compare SSTF to FCFS, LOOK to FCFS, and LOOK to SSTF.

As in our previous question, when the first request arrives in the disk request queue, the read/write head is at track 50, moving toward the outer (lower-numbered) tracks.

The requested tracks are:

35, 53, 90, 67, 79, 37, 76, 47