How many sub strings can be formed from a character string of length $$n$$?

Which of the following graphs is / are planar? (see fig.)

Match the pairs in the following question.

List - $${\rm I}$$
$$(A)$$$$\,\,\,\,$$ Virtual Memory
$$(B)$$$$\,\,\,\,$$ Shared memory
$$(C)$$$$\,\,\,\,$$ Look-ahead buffer
$$(D)$$$$\,\,\,\,$$ Look-aside buffer

List - $${\rm II}$$
$$(p)$$$$\,\,\,\,$$ Temporal locality
$$(q)$$$$\,\,\,\,$$ Spatial Locality
$$(r)$$$$\,\,\,\,$$ Address Translation
$$(s)$$$$\,\,\,\,$$ Mutual exclusion

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.