Prove Theorem 3 as follows: Given an m % n matrix A, an element in Col A has the form Ax for some x in Rn. Let Ax and Aw represent any two vectors in Col A. a. Explain why the zero vector is in Col A. b. Show that the vector Ax C Aw is in Col A. c. Given a scalar c, show that c.Ax/ is in Col A