Consider the following premises. r_1 <-> s_4. ~s_4. t. s <-> r_1. Can we infer t and ~s from them?
 From r_1 <-> s_4, ~s_4 we can infer ~r_1. From s <-> r_1, ~r_1 we can infer ~s. Finally, from t, ~s we can infer t and ~s. Therefore, the answer is yes.