4. For each of the following languages below, are they RE or recursive? Justify your answer. a) The set of (codes of) Turing machines that use at most 20 tape cells starting from an all blank tape. b) The set of (codes of) Turing machines M such that M accepts at least one palindrome w (for which ww ). 4. For each of the following languages below, are they RE or recursive? Justify your answer. a) The set of (codes of) Turing machines that use at most 20 tape cells starting from an all blank tape. b) The set of (codes of) Turing machines M such that M accepts at least one palindrome w (for which ww )