$(12$ points$)$ Quicksort

a$.$ Using the first element as the pivot, sort $6,3,8,5,1,4,9,5,2,7,5$ using quicksort, show the

result after each of first$-$two round partitions.

b$.$ Here is an array which has just been partitioned by the first step of quicksort $($the pivot

element har already besn swapped with the element pointed to by $i$ in the final part of the

partitioning$)$:

$0,3,2,4,5,8,7,6,9$

List ALL possible pivots.