Consider the following premises. forall x_9: R_9(x_9) <-> S_9(x_9). R_9(a_9) -> S_9(a_9). Can we infer S_9(a_9) -> R_9(a_9) from them? If possible, name the inference rules being used at each step.
 From forall x_9: R_9(x_9) <-> S_9(x_9) we can infer R_9(a_9) <-> S_9(a_9) via universal instantiation. Finally, from R_9(a_9) <-> S_9(a_9) we can infer S_9(a_9) -> R_9(a_9) via biconditional elimination. Therefore, the answer is yes.