(d) Merge sort is a well-known divide-and-conquer approach based on recursively splitting an input array into two sub-arrays of roughly half the size (divide stage) and then merging the sorted sub-arrays to sort the original input (conquer stage). Consider a variant of the merge sort algorithm which proceeds by recursively splitting the array into three sub-arrays of roughly a third of the size during the divide stage and then merging the sorted sub-arrays to sort the original input array during the conquer stage. [10%) Solve it to express the computational complexity as a function of the variable N. (20%)