Consider the following premises. r_1. forall x_18: P_18(x_18). w_4 -> ~r_1. Can we infer w_4 from them? If possible, name the inference rules being used at each step.
 From forall x_18: P_18(x_18) we can infer P_18(a_18) via universal instantiation. Finally, from w_4 -> ~r_1, r_1 we can infer ~w_4 via modus tollens, which contradicts w_4. Therefore, the answer is no.