4. (15 marks) Let the universe for the variables in the following statements consist of all real numbers. In each case, indicate whether the given statement is true or false and briefly justify or ch wte the gatie possible (a) VzVyVz, ((z-y-z-z) (y = z)) (b) VzVyYz, ((z-y = xz) ((z0) (y = z))) (c) Vz, (z 2 0 (3, (y-z))) (e) Vz3y, (x + 5 = y)