Please explain your answer, no code needed just give the algorithm(steps)

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(2-D maximum-sum subarray) (30 points) In the 2-D Maximum-Sum Subarray Problem, you are given a two-dimensional mn array A[1:m,1:n] of positive and negative numbers, and you are asked to find a subarray A[a:b,c:d], where 1abm and 1cdn, such that the sum of its elements, aibcjdA[i,j], is maximum. (a) (30 points) Using exhaustive search, design an algorithm that runs in O(m2n2) time using O(min{m,n}) working space. The working space of an algorithm is the memory it uses beyond what is needed to store the input. (Hint: First design a straightforward algorithm that achieves O(m3n3) time, and then optimize it.)