Consider the following premises. p_4. q_11. s -> ~q_11. s <-> q_4. Can we infer q_4 from them? If possible, name the inference rules being used at each step.
 From s -> ~q_11, q_11 we can infer ~s via modus tollens. Finally, from s <-> q_4, ~s we can infer ~q_4 via biconditional elimination, which contradicts q_4. Therefore, the answer is no.