Disk requests come to disk driver for cylinders $$10,22,20,2,40,56$$ and $$38,$$ in that order at a time when the disk drive is reading from cylinder $$20.$$ The seek time is $$6msec$$ per cylinder. Compute the total seek time if the disk arm scheduling algorithm is
(a) First come first served
(b) Closest cylinder next.

On receiving an interrupt from an $${\rm I}/O$$ device the $$CPU$$: