Consider the following premises. forall x: W(x) <-> U(x). t <-> U(j). forall x: ~W(x). Can we infer t from them? If possible, name the inference rules being used at each step.
 From forall x: W(x) <-> U(x), forall x: ~W(x) we can infer forall x: ~U(x) via universal biconditional elimination. From forall x: ~U(x) we can infer ~U(j) via universal instantiation. Finally, from t <-> U(j), ~U(j) we can infer ~t via biconditional elimination, which contradicts t. Therefore, the answer is no.