the result in (c)? 3. What is the dimension of the null matrix resulting from each of the following? (a) Premultiply A by a 5 x 2 null matrix (b) Postmultiply A by a 3 x 6 null matrix. (c) Premultiply b by a 2 x 3 null matrix. (d) Postmultiply x by a 1 x 5 null matrix. 4. Show that the diagonal matrix 011 0