Answer
The new rotational speed is $7,200$ rev/min $=120 \mathrm{rev} / \mathrm{sec}=8.33$ msec/rev.
The seek time is unaffected by the rotational speed. The new average
latency time is 0.5 rev $\times 8.33$ msec/rev $=4.17$ msec. The new transfer
time is 1$/ 20$ rev $\times 8.33$ msec/rev $=0.42$ msec. The total average case
time $=12.59$ msec.
Work Step by Step
The new rotational speed is $7,200$ rev/min $=120 \mathrm{rev} / \mathrm{sec}=8.33$ msec/rev.
The seek time is unaffected by the rotational speed. The new average
latency time is 0.5 rev $\times 8.33$ msec/rev $=4.17$ msec. The new transfer
time is 1$/ 20$ rev $\times 8.33$ msec/rev $=0.42$ msec. The total average case
time $=12.59$ msec.
