Consider the following premises. s_4 <-> t. t or ~p. ~s_4. Can we infer ~p from them? If possible, name the inference rules being used at each step.
 From t or ~p we can infer p -> t via rewriting. From s_4 <-> t, ~s_4 we can infer ~t via biconditional elimination. Finally, from p -> t, ~t we can infer ~p via modus tollens. Therefore, the answer is yes.