Consider the following premises. w_1 or p_4. ~w_1 or s_1. forall z: ~U_1(z). p_4 -> U_1(c). Can we infer ~s_1 from them? If possible, name the inference rules being used at each step.
 From forall z: ~U_1(z) we can infer ~U_1(c) via universal instantiation. From p_4 -> U_1(c), ~U_1(c) we can infer ~p_4 via modus tollens. From w_1 or p_4, ~w_1 or s_1 we can infer p_4 or s_1 via resolution. Finally, from p_4 or s_1, ~p_4 we can infer s_1 via disjunctive syllogism, which contradicts ~s_1. Therefore, the answer is no.