Consider the following premises. s_3 or u_4. p or q_9. s_3 -> ~q_9. ~p. Can we infer ~u_4 from them? If possible, name the inference rules being used at each step.
 From p or q_9, ~p we can infer q_9 via disjunctive syllogism. From s_3 -> ~q_9, q_9 we can infer ~s_3 via modus tollens. Finally, from s_3 or u_4, ~s_3 we can infer u_4 via disjunctive syllogism, which contradicts ~u_4. Therefore, the answer is no.