Let $M$ be a $7\times6$ real matrix. The entries of $M$ in the positions $(1, 3), (1, 4), (3, 3), (3, 4)$, and $(5, 4)$ are changed to obtain another $7\times6$ real matrix $N$ . Suppose that the rank of $N$ is $4$. What could be the rank of $M$ ?

I know that changing a single element of a matrix, rank can change at most one.