3. Let u(r) represent some consumer's monotonic preferences over a E R4. For each function of f(x) that follow, state whether or not f also represents the preferences of this consumer. In each case be sure to justify your answer with either an argument or a counterexample. (a) f(x) = u(x) + (u(x)) (b) f(x) = u(x) + (u(x))2 (c) f(x) = u(x) + Ex