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_13 <-> w. u -> r_1. w -> u. r_1 -> p_13.
u -> p_13 can be inferred via the transitivity rule. w -> r_1 can be inferred via the transitivity rule. p_13 -> w can be inferred via the biconditional elimination rule. w -> p_13 can be inferred via the biconditional elimination rule.