5. (a) Let a,ce " be unit vectors. Show that there is a unitary matrix U such that 1 ac 0 1 - a*c12 U 0 0 : 0 0 (b) Let a, b, c, d e C be unit vectors. Let X = ab*, Y = cd* M.(C). As X and Y are rank one matrices, rank (XY - YX)