a. Suppose that a disk drive has 10,000 cylinders, numbered 0 to 9999. The driver is currently serving a request at cylinder 1400. The queue of pending requests is, in the order received: 100, 1200, 900, 8000, 8100, 100, 8200, 1000, 4200 Starting from the current head position, what is the total distance (in cylinders) that the disk arm moves to satisfy all the pending requests for the following scheduling algorithms. (For the algorithms in which the head is in constant motion, indicate the direction in which you assume it is moving initially.) (1) FCFS (ii) SSTF (iii) SCAN (iv) C-LOOK [12 marks] [3 marks] b. Explain the purpose of the open() and close() operations. c. Briefly explain any two types of virtualization [4 marks] d. Allocation/replacement of frames among different processes can either be local or global. What do you understand by this? What could be a possible effect of using the later(global replacement) [6 marks]