What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? ~t. r_1 -> q_11. q_11 <-> u_2. u_2 -> t. q_11 -> r_1.
~u_2. r_1 <-> q_11. q_11 <-> r_1. q_11 -> u_2. u_2 -> q_11.