Quicksort performed worst if the position of pivot is either first or last.
By the above discussion, I conclude that there are two worst-case positions first or the last position.
Probability = 2/25=0.04
It can also understand as if we choose a minimum or maximum element as a pivot because if we choose minimum as pivot then it will be placed at a first position or if we choose the last element as pivot then it will be placed at the last position. So the probability is= 2/25=0.04