Consider the following premises. t <-> p_2. p_2 -> ~r_4. R_19(b) or r_4. forall x_19: ~R_19(x_19). Can we infer t from them? If possible, name the inference rules being used at each step.
 From forall x_19: ~R_19(x_19) we can infer ~R_19(b) via universal instantiation. From R_19(b) or r_4, ~R_19(b) we can infer r_4 via disjunctive syllogism. From p_2 -> ~r_4, r_4 we can infer ~p_2 via modus tollens. Finally, from t <-> p_2, ~p_2 we can infer ~t via biconditional elimination, which contradicts t. Therefore, the answer is no.