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: forall x_15: T(x_15) -> S_15(x_15). ~S_15(a_15). s <-> T(a_15).
s -> T(a_15) can be inferred via the biconditional elimination rule. T(a_15) -> s can be inferred via the biconditional elimination rule.