Consider the string (y)(x1 = y1 ((z)f(z) = x1 (z)f(z) = y1)).

(a) Show this string is a well-formed formula. Hint. Use bottom-up or top-down parsing. (b) Is this well-formed formula a tautology? Show all work and remember that to show that a schema is not a tautology we must identify an instance of it that is not a tautology.