Problem 4.6 A system of linear equations Ax = d is known to have lthe following solution: 1 2 l 2 l l x: 1) +3 T +1 0 , SJER. l 0 1 '0 O 1 Assume that A is an m x n matrix. Let c1, cg, c\" denote the columns of A. Answer each of the following questions or, if there is insufcient (1) (2) (3) (4) (5) information to answer a question, say so. What number is n? What number is m? What (number) is the rank of A? Describe the null space N (A). Write down an expression for d as a linear combination of the columns of A