Consider a disk with N tracks numbered from 0 to (N - 1) and assume that requested sectors are distributed randomly and evenly over the disk. We want to calculate the average number of tracks traversed by a seek.  a. First, calculate the probability of a seek of length j when the head is currently positioned over track t. Hint: This is a matter of determining the total number of combinations, recognizing that all track positions for the destination of the seek are equally likely.  b. Next, calculate the probability of a seek of length K. Hint: this involves the summing over all possible combinations of movements of K tracks.