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_2 <-> w. r_2 <-> w.
r_2 -> w can be inferred via the biconditional elimination rule. r_2 -> w can be inferred via the biconditional elimination rule. w -> r_2 can be inferred via the biconditional elimination rule. w -> r_2 can be inferred via the biconditional elimination rule.