Consider the following premises. p_2 <-> s_4. r -> s_4. ~p_2. r <-> w. Can we infer w from them? If possible, name the inference rules being used at each step.
 From p_2 <-> s_4, ~p_2 we can infer ~s_4 via biconditional elimination. From r -> s_4, ~s_4 we can infer ~r via modus tollens. Finally, from r <-> w, ~r we can infer ~w via biconditional elimination, which contradicts w. Therefore, the answer is no.