4. Determine, with proof, which of the following languages are undecidable. That is, for an undecidable language, present a proof via Turing reduction of its undecidability, and for a decidable language, exhibit a decider for that language. (a) LALTERNATE = {.x : neither 00 nor 11 is a substring of x} (b) LEVEN = {(M): L(M) is even} (c) L376-HALT = {((M), 2) : M halts on x in 2|376 steps} (d) LQUICK-HALT = {(M) : There is an input w such that M halts on w within w steps Hint: See hint in Question 1. 4. Determine, with proof, which of the following languages are undecidable. That is, for an undecidable language, present a proof via Turing reduction of its undecidability, and for a decidable language, exhibit a decider for that language. (a) LALTERNATE = {.x : neither 00 nor 11 is a substring of x} (b) LEVEN = {(M): L(M) is even} (c) L376-HALT = {((M), 2) : M halts on x in 2|376 steps} (d) LQUICK-HALT = {(M) : There is an input w such that M halts on w within w steps Hint: See hint in Question 1