4. (5 points) [B,D] The string reversal operation takes as input a strings and outputs the same string in reverse order. For example (abcde)" = edcba. The language reversal operation takes as input a language L and produces as output a new language LR consisting of all the string reversals of strings in L. For example {abc, aa} = {cba, aa}. (a) (1 point) [B] Express the closure property that RE is closed under language reversal in first-order logic. (b) (2 points) [B] Give the generic element proof outline that RE is closed under language reversal. (c) (2 points) [D] Give pseudocode for the main procedure of the program that is part of this proof.