Consider the following premises. u -> t. t -> S_12(a_12). forall x_12: R_12(x_12) <-> S_12(x_12). Can we infer u -> R_12(a_12) from them? If possible, name the inference rules being used at each step.
 From forall x_12: R_12(x_12) <-> S_12(x_12) we can infer R_12(a_12) <-> S_12(a_12) via universal instantiation. From u -> t, t -> S_12(a_12) we can infer u -> S_12(a_12) via transitivity. From R_12(a_12) <-> S_12(a_12) we can infer S_12(a_12) -> R_12(a_12) via biconditional elimination. Finally, from u -> S_12(a_12), S_12(a_12) -> R_12(a_12) we can infer u -> R_12(a_12) via transitivity. Therefore, the answer is yes.