Consider the following premises. q_4 <-> q_12. s_4 <-> q_12. ~s_4. ~q_4 -> s. Can we infer s from them? If possible, name the inference rules being used at each step.
 From s_4 <-> q_12, ~s_4 we can infer ~q_12 via biconditional elimination. From q_4 <-> q_12, ~q_12 we can infer ~q_4 via biconditional elimination. Finally, from ~q_4 -> s, ~q_4 we can infer s via modus ponens. Therefore, the answer is yes.