4. (1 point) An m x n matrix A is said to have the right inverse if there exists an m x n matrix C such that AC = Im. The matrix A is said to have the left inverse is there exists an n x m matrix D such that DA = 1 (a) Prove that if A has a right inverse then the columns of A span R. (b) Is it possible for an m x n matrix to have a right inverse if n < m?n? m? Explain. (c) Prove: If the columns of A span R™ then A has a right inverse.