Consider the following premises. p_4. ~q_13. p <-> s. p <-> q_13. Can we infer ~s and p_4 from them?
 From p <-> q_13, ~q_13 we can infer ~p. From p <-> s, ~p we can infer ~s. Finally, from ~s, p_4 we can infer ~s and p_4. Therefore, the answer is yes.