Let (a) Find the reduced row echelon form of the matrix B rref(B)- (b) How many pivot columns does B have? (c) Do the vectors in the set {AGE} {AGE} choose (d) Are the vectors in the set 3 B 6 -3-9 3 4 2 span R7 Be sure you can explain and justify your answer. linearly independent? Be sure you can explain and justify your answer.