Consider the following premises. s_3 -> t_1. s or r_2. s -> s_3. t -> ~t_1. r_2 -> s_3. Can we infer ~t from them?
 From s -> s_3, r_2 -> s_3, s or r_2 we can infer s_3. From s_3 -> t_1, s_3 we can infer t_1. Finally, from t -> ~t_1, t_1 we can infer ~t. Therefore, the answer is yes.