3. Consider the following matrix 2 -4 0 -2 -3 4 1 2 A = 0 1 2 1 4 -2 -3 -1 a) How many rows of this matrix contain a pivot position? Does the equation Ax = b have a solution for each b in R^? b) Can each vector in R4 be written as a linear combination of the columns of matrix A above? Do the columns of A span R4? c) Choose one of the columns of matrix A. Can you write that column as a linear combination of the other three columns? If yes, please write. If no, why?