Consider the following premises. forall x_13: W_4(x_13) -> R(x_13). forall x_13: U(x_13) <-> Q_13(x_13). forall x_13: W_4(x_13) -> Q_13(x_13). forall x_13: Q_13(x_13) -> W_4(x_13). Can we infer exists x_13: ~(U(x_13) -> R(x_13)) from them?
 From forall x_13: W_4(x_13) -> Q_13(x_13), forall x_13: Q_13(x_13) -> W_4(x_13) we can infer forall x_13: W_4(x_13) <-> Q_13(x_13). From forall x_13: U(x_13) <-> Q_13(x_13) we can infer forall x_13: U(x_13) -> Q_13(x_13). From forall x_13: W_4(x_13) <-> Q_13(x_13) we can infer forall x_13: Q_13(x_13) -> W_4(x_13). From forall x_13: U(x_13) -> Q_13(x_13), forall x_13: Q_13(x_13) -> W_4(x_13) we can infer forall x_13: U(x_13) -> W_4(x_13). Finally, from forall x_13: U(x_13) -> W_4(x_13), forall x_13: W_4(x_13) -> R(x_13) we can infer forall x_13: U(x_13) -> R(x_13), which contradicts exists x_13: ~(U(x_13) -> R(x_13)). Therefore, the answer is no.