Consider the following premises. p_6. p_6 <-> s_4. ~s_4. Can we infer q from them?
 From p_6 we can infer p_6 or q. From p_6 <-> s_4, ~s_4 we can infer ~p_6. Finally, from p_6 or q, ~p_6 we can infer q. Therefore, the answer is yes. Notice, however, that the premises were contradictory, so we can infer anything from them.