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_3 <-> r_1. r_1 or ~u_4. p_3 or q. q -> u_4.
u_4 -> r_1 can be inferred via the rewriting rule. p_3 -> r_1 can be inferred via the biconditional elimination rule. r_1 -> p_3 can be inferred via the biconditional elimination rule.