Consider the following premises. S_12(f) -> w. w -> S_12(f). ~w. forall x_12: R_12(x_12) -> S_12(x_12). Can we infer R_12(f) 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(f) -> S_12(f) via universal instantiation. From S_12(f) -> w, w -> S_12(f) we can infer S_12(f) <-> w via biconditional introduction. From S_12(f) <-> w, ~w we can infer ~S_12(f) via biconditional elimination. Finally, from R_12(f) -> S_12(f), ~S_12(f) we can infer ~R_12(f) via modus tollens, which contradicts R_12(f). Therefore, the answer is no.