Consider the following premises. ~u_2. p <-> r. r <-> u_2. Can we infer p from them? If possible, name the inference rules being used at each step.
 From r <-> u_2, ~u_2 we can infer ~r via biconditional elimination. Finally, from p <-> r, ~r we can infer ~p via biconditional elimination, which contradicts p. Therefore, the answer is no.