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: w_2 -> s. p_18 -> s. w_2 or w. p_18 <-> w.
p_18 -> w can be inferred via the biconditional elimination rule. w -> p_18 can be inferred via the biconditional elimination rule.