What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? q_4. ~r. u_1 <-> r. t_4 -> u_1. u_1 -> t_4.
q_4 and ~r. ~r and q_4. t_4 <-> u_1. u_1 <-> t_4. u_1 -> r. r -> u_1. ~u_1.