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: forall x_11: U(x_11) or S_11(x_11). ~U(b) or r_7. u_4 <-> q_15. ~q_15. S_11(b) -> u_4.
u_4 -> q_15 can be inferred via the biconditional elimination rule. q_15 -> u_4 can be inferred via the biconditional elimination rule. ~u_4 can be inferred via the biconditional elimination rule.