Consider the following premises. S_9(a_9) -> u. ~u. forall x_9: R_9(x_9) <-> S_9(x_9). u -> S_9(a_9). Can we infer 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. From u -> S_9(a_9), S_9(a_9) -> u we can infer u <-> S_9(a_9) via biconditional introduction. From u <-> S_9(a_9), ~u we can infer ~S_9(a_9) via biconditional elimination. Finally, from R_9(a_9) <-> S_9(a_9), ~S_9(a_9) we can infer ~R_9(a_9) via biconditional elimination, which contradicts R_9(a_9). Therefore, the answer is no.