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_1 -> s. p_3 <-> u_1. s -> q. ~p_3. q -> u_1.
u_1 -> q can be inferred via the transitivity rule. s -> u_1 can be inferred via the transitivity rule. q -> s can be inferred via the transitivity rule. p_3 -> u_1 can be inferred via the biconditional elimination rule. u_1 -> p_3 can be inferred via the biconditional elimination rule. ~u_1 can be inferred via the biconditional elimination rule.