$11\mathrm{.}8.$Consider the disk system described in Problem $11\mathrm{.}7,$ and assume that the disk rotates at $1,200$ rpm$.$ A processor reads one sector from the disk using interrupt$-$driven I$/$O$,$ with one interrupt every $4$ bytes. If it takes $1\mathrm{.}5$ s to process each interrupt, what percentage of the time will the processor spend handling I$/$O $($disregard seek time$)?$

$11\mathrm{.}9.$Repeat the preceding problem using DMA, and assume one interrupt per sector.