Consider the following premises. ~u_4. p_6 <-> u_4. p_6 -> p. p -> p_6. Can we infer p from them?
 From p_6 <-> u_4, ~u_4 we can infer ~p_6. From p_6 -> p, p -> p_6 we can infer p_6 <-> p. Finally, from p_6 <-> p, ~p_6 we can infer ~p, which contradicts p. Therefore, the answer is no.