An application loads 100 libraries at startup. Loading each library requires exactly one disk access. The seek time of the disk to a random location is given as 10 ms. Rotational speed of disk is 6000 rpm. If all 100 libraries are loaded from random locations on the disk, how long does it take to load all libraries? (The time to transfer data from the disk block once the head has been positioned at the start of the block may be neglected.)

1. Rotational Latency Calculation:

   • Rotational speed $= 6000\text{ rpm} = \frac{6000}{60}\text{ rps} = 100\text{ revolutions/second}$.

   • Time for one full revolution $= \frac{1}{100}\text{ s} = 10\text{ ms}$.

   • Average rotational latency $= \frac{1}{2} \times \text{Time for one revolution} = \frac{10\text{ ms}}{2} = 5\text{ ms}$.

2. Time for one disk access:

   $$\text{Access Time} = \text{Seek Time} + \text{Average Rotational Latency} + \text{Transfer Time}$$

   $$\text{Access Time} = 10\text{ ms} + 5\text{ ms} + 0\text{ ms} = 15\text{ ms}$$

3. Total time to load 100 libraries:

   $$\text{Total Time} = 100 \times 15\text{ ms} = 1500\text{ ms} = 1.50\text{ s}$$

Hence, it takes 1.50 s to load all libraries, which is option (B).