Consider a disk system with cylinders. The request to access the cylinders occurs in the following sequence: 4, 34, 10, 7, 19, 73, 2, 15, 6, 20 Assuming that the head is currently at cylinder 50 , what is the time taken to satisfy all requests if it takes 1 ms to move from one cylinder to adjacent one and shortest seek time first policy is used?

1. A119 ms
2. B120 ms
3. C142 ms
4. D146 ms

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Correct answer: A. 119 ms

Explanation

From 50: 34 (16), 20 (14), 19 (1), 15 (4), 10 (5), 7 (3), 6 (1), 4 (2), 2 (2), then 73 (71). Total = 119 cylinders × 1 ms = 119 ms.