Consider the following premises. t or ~q_5. ~u_4. u_4 <-> p. ~p -> t. Can we infer ~t from them?
 From u_4 <-> p, ~u_4 we can infer ~p. From t or ~q_5 we can infer q_5 -> t. From ~p we can infer ~p or q_5. Finally, from ~p -> t, q_5 -> t, ~p or q_5 we can infer t, which contradicts ~t. Therefore, the answer is no.