Consider the following premises. ~r_1. p_9 <-> t. p_9 -> r_1. Can we infer t from them?
 From p_9 <-> t we can infer t -> p_9. From t -> p_9, p_9 -> r_1 we can infer t -> r_1. Finally, from t -> r_1, ~r_1 we can infer ~t, which contradicts t. Therefore, the answer is no.