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: ~r_4. S_15(a_15) <-> s. r_4 <-> s. forall x_15: R_15(x_15) -> S_15(x_15).
S_15(a_15) -> s can be inferred via the biconditional elimination rule. r_4 -> s can be inferred via the biconditional elimination rule. s -> S_15(a_15) can be inferred via the biconditional elimination rule. s -> r_4 can be inferred via the biconditional elimination rule. ~s can be inferred via the biconditional elimination rule.