Consider the following premises. p_4 <-> q_7. p_4 -> p_1. ~p_1. Can we infer q_7 from them?
 From p_4 -> p_1, ~p_1 we can infer ~p_4. Finally, from p_4 <-> q_7, ~p_4 we can infer ~q_7, which contradicts q_7. Therefore, the answer is no.