What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Name the inference rule being used: p. forall x_13: R_13(x_13) <-> S_13(x_13). ~S_13(a_13).
p and ~S_13(a_13) can be inferred via the conjunction rule. ~S_13(a_13) and p can be inferred via the conjunction rule. forall x_13: R_13(x_13) -> S_13(x_13) can be inferred via the universal biconditional elimination rule. forall x_13: S_13(x_13) -> R_13(x_13) can be inferred via the universal biconditional elimination rule.