Consider the following premises. q_6 -> r_6. ~r_6. p <-> p_4. p_4 -> q_6. Can we infer p from them?
 From p_4 -> q_6, q_6 -> r_6 we can infer p_4 -> r_6. From p_4 -> r_6, ~r_6 we can infer ~p_4. Finally, from p <-> p_4, ~p_4 we can infer ~p, which contradicts p. Therefore, the answer is no.