A hard disk of $20$ sectors per track and $400$ tracks per surface in $15$ double$-$sided platters disk, and platters rotates at a speed of $2400$ RPM with average seek time $30$ ms$.$ Each sector contains a block of size $512$ bytes and gap size between blocks $128$ bytes. What is the total useful capacity of a track?Select one:a$.$ noneb. $8$ KBc$.4\mathrm{.}096$ KBd$.10240$ Bytese. $12\mathrm{.}5$ KB