Consider a hard disk drive with $10$ platters of $3\mathrm{.}5$ inches in diameter, $256$ Cylinders,

usable capacity of $10GB,$ block size of $4KB,20\%$ gaps between blocks, average seek

time of $20ms,$ rotation speed of $3840$ round per minute$($RPM$)$ and assume tracks

occupy the outer $1$ inch of surfaces. Suppose the head assembly is currently on

cylinder $75.$ What is the expected number of cylinders to travel over in order to

process the next disk I$/$O request? Hint: Consider all cylinders that could possibly

hold the requested data block?