Given a $n \times n$ matrix $M$ of positive integers and a constant $d$. If $R,C \subset \{1,...,n\} $ let $$S_M(R,C) = \sum_{r \in R,c \in C }M_{i,j} $$
I want to find the sets $$R,C \subset \{1,...,n\}, |R|,|C| = d $$ such that $S_M(R,C)$ is as big as possible.
I suspect this to be a known problem. I am wondering if anyone has seen this before and can point me towards research papers on this problem