Disk perform 6000 Rotation 60 sec.
1 " $\frac{1}{100}$
$\frac{1}{2}$ " $\frac{1}{100}\times \frac{1}{2}$ sec.=5 ms.
Time required for 1 rotation=10 ms.
64 sector rotates in 10 ms.
1 " " " $\frac{10}{64}$ ms.
800 " " "$\frac{10}{64}\times 800$=125 ms.
$\frac{10}{64}$ ms. work done 1 KB
1 ms. " " $\frac{64}{10}$ KB
1000 ms. " "$\frac{64}{10}\times 1000$=6400 KB.
S1: is correct
S2:is incorrect, as we cannot calculate read time of random sector, because the read write head can move from 1 sector to next successive sector only.
S3: is incorrect , as time required for 800 successive sector is .125 sec.
Ans D)