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: p -> r_3. r_3 -> p. r_3 -> p.
p <-> r_3 can be inferred via the biconditional introduction rule. p <-> r_3 can be inferred via the biconditional introduction rule. r_3 <-> p can be inferred via the biconditional introduction rule. r_3 <-> p can be inferred via the biconditional introduction rule.