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