k-Way Merge Operation

Suppose you have k sorted arrays, each with n elements, and you want to combine them into a single sorted array of kn elements.

(a) Heres one strategy: Using the merge procedure from the merge-sort algorithm, merge the first two arrays, then merge in the third, then merge in the fourth, and so on. What is the time complexity of this algorithm, in terms of k and n?

(b) Give a more efficient solution to this problem, using divide-and-conquer