In merge sort analysis, we used the recursion tree method. What is the pattern in that recursion tree? Fill in the blanks in the following statement: at each levelj = 0, 1, 2, ... of the recursion tree, there are [blank] subproblems, each operating on a subarray of length [blank]. O2 and 2respectively On2 and 1/2, respectively O2 and n/2 respectively On2 and 2) respectively