4. Suppose that a hard disk's heads are at cylinder 50 and requests have been queued for the following cylinders: 1, 57, 46, 104, 18, 60, 93, 32, 112. a. Give the order and the total number cylinders of seek done for FCFS. b. Repeat (a) for SSTF. c. Repeat (a) for Elevator (assume the initial direction is decreasing). d. Why is the Elevator algorithm often modified to serve requests in only one direction? e. Give two circumstances under which it does not make sense for the disk driver to perform scheduling to optimize seek time. Explain.