Consider the following premises. q_1 <-> p_1. ~q_1. t -> p_1. p_1 -> t. Can we infer ~t from them?
 From p_1 -> t, t -> p_1 we can infer p_1 <-> t. From q_1 <-> p_1 we can infer p_1 -> q_1. From p_1 -> q_1, ~q_1 we can infer ~p_1. Finally, from p_1 <-> t, ~p_1 we can infer ~t. Therefore, the answer is yes.