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. r_2 -> r. r_2 or s. p_13 <-> r. s -> r.
r can be inferred via the disjunction elimination rule. p_13 -> r can be inferred via the biconditional elimination rule. r -> p_13 can be inferred via the biconditional elimination rule.