Consider the following premises. q_4 -> t. q_4 <-> q_14. ~q_9. t <-> q_9. Can we infer q_14 from them? If possible, name the inference rules being used at each step.
 From q_4 <-> q_14 we can infer q_14 -> q_4 via biconditional elimination. From t <-> q_9, ~q_9 we can infer ~t via biconditional elimination. From q_4 -> t, ~t we can infer ~q_4 via modus tollens. Finally, from q_14 -> q_4, ~q_4 we can infer ~q_14 via modus tollens, which contradicts q_14. Therefore, the answer is no.