Consider the following premises. s or s_4. s_4 -> q_3. p -> q. q -> ~q_3. s -> q_3. Can we infer p from them? If possible, name the inference rules being used at each step.
 From s -> q_3, s_4 -> q_3, s or s_4 we can infer q_3 via disjunction elimination. From q -> ~q_3, q_3 we can infer ~q via modus tollens. Finally, from p -> q, ~q we can infer ~p via modus tollens, which contradicts p. Therefore, the answer is no.