Consider an n×m matrix A. For which positive integers j = 1, . . . ,m does there exist a...

Consider an n×m matrix A. For which positive integers j = 1, . . . ,m does there exist a vector in the kernel of A such that the j th component x _j of is nonzero, while all the components x _j+1, . . . , x_m are zero? Use Exercise 57 as a guide. Give your answer in terms of the redundant column vectors of A.