Maximum Sum Rectangle Problem

Given an M x N matrix of integers ARR, your task is to identify the rectangle within the matrix that has the greatest sum of its elements.

Input:

The first line of input contains an integer 'T' representing the number of test cases. For each test case, the first line contains two space-separated integers, M and N, indicating the dimensions of the matrix ARR. The following M lines each contain N space-separated integers, representing the elements of the matrix ARR.

Output:

For each test case, return the maximum sum obtained from any rectangle within the matrix.

Example:

Input:

1
4 5
1 2 -1 -4 -20
-8 -3 4 2 1
3 8 10 1 3
-4 -1 1 7 -6

Output:

29

Explanation:

The submatrix from (1,1) to (3,3) has the maximum sum of 29, illustrated as:

 1   2 -1 -4  -20
-8 |-3  4  2 |  1
 3 | 8  10 1 |  3
-4 |-1  1  7 | -6

Constraints:

• 1 ≤ T ≤ 10
• 1 ≤ M, N ≤ 100
• -105 ≤ ARR[i] ≤ 105

Note: You do not need to print anything; implement the function to return the result only.