Consider the following premises. forall x: R(x) -> U(x). U(h) <-> R(h). ~R(h). Can we infer U(h) from them? If possible, name the inference rules being used at each step.
 From forall x: R(x) -> U(x) we can infer R(h) -> U(h) via universal instantiation. From U(h) <-> R(h) we can infer U(h) -> R(h) via biconditional elimination. From R(h) -> U(h), U(h) -> R(h) we can infer R(h) <-> U(h) via biconditional introduction. Finally, from R(h) <-> U(h), ~R(h) we can infer ~U(h) via biconditional elimination, which contradicts U(h). Therefore, the answer is no.