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 <-> u_1. q_1 -> u_1. r -> q_1.
r -> u_1 can be inferred via the transitivity rule. r -> u_1 can be inferred via the biconditional elimination rule. u_1 -> r can be inferred via the biconditional elimination rule.