The truth value of a logical expression is defined recursively as: The truth value of t is t. The truth value of f is f . The truth value of ( ^T2) is t if both 11 and 2.2 have truth value t, it is f otherwise. . The truth value of (z.vx2) is f if both ri and 2.2 have truth value f, it is t otherwise. The truth value of-'(z) is f ir has truth value t, it is t otherwise. Define a CFG that generates the following language over(t,f, A, V, (.), {w=x : u, is a logical expression over {t, f}, r E {t, f}, and r is the truth value of w} Thus, "t = t" , "((t ^ f) v f)-f" , and-(((tA f) v f))-t" are in L, but "((tA f)v f)-t" and (tA f) v f- f" are not: the former because ((t A f)V f) is false and not true, the latter because the expression lacks the outermost set of parentheses