Exercise 4 (2 pts). Give an example of two languages A and B such that both A and B are undecidable, AUB is decidable. Exercise 5 (bonus 2 pts). Theorem 5.2 in the textbook says that the language Erm is ndecidable. Use the undecidability of ETH to prove that the following language L is unde- dable: L = {(MM) M and My are TMs such that L(M) CL(M)}. Exercise 4 (2 pts). Give an example of two languages A and B such that both A and B are undecidable, AUB is decidable. Exercise 5 (bonus 2 pts). Theorem 5.2 in the textbook says that the language Erm is ndecidable. Use the undecidability of ETH to prove that the following language L is unde- dable: L = {(MM) M and My are TMs such that L(M) CL(M)}