Consider the following premises. s_1 <-> q_4. t -> s_1. ~q_4. s_1 -> t. Can we infer ~t from them?
 From s_1 <-> q_4, ~q_4 we can infer ~s_1. From s_1 -> t, t -> s_1 we can infer s_1 <-> t. From s_1 <-> t we can infer t -> s_1. Finally, from t -> s_1, ~s_1 we can infer ~t. Therefore, the answer is yes.