What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? ~u_3. t_4 <-> t_3. t_3 <-> u_3. ~t_4 -> t_1.
t_4 -> t_3. t_3 -> u_3. t_3 -> t_4. u_3 -> t_3. ~t_3.