Problem 9. Suppose U{A} is a satisfiable set of formulae and FU{A}U {B} \taut 1. Is it necessarily the case that T \taut B? Prove or give a counterexample. Hint. It is in fact the case that \taut B. So you should prove that taut B is incorrect. You can proceed by either giving a counterexample or proof by contradiction. The latter means assume =taut B and reach to a contradiction with the other two assumptions.