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: u -> p_1. p_1 <-> q_7. q_7.
p_1 -> q_7 can be inferred via the biconditional elimination rule. q_7 -> p_1 can be inferred via the biconditional elimination rule.