A computer has a hard disk that rotates with a speed of $7200$ RPM $($rotations per minute$),$ and him a reported seek time of $5ms$ and transfer time of $2$MByte$\frac{5}{s}.$ The hard disk has $8$ platters, $1za$ tracks per platter, $256$ sectors per track, and each sector has $512$ bytes.

$[5$ marks$]$

a$.$ What is the average access time of the hard disk, in ms$?$

b$.$ What is the capacity of the hard disk, in Mbytes?