What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? q_20 -> t_4. ~w. p. q_20 <-> w. t_4 -> q_20.
~w and p. p and ~w. q_20 <-> t_4. t_4 <-> q_20. q_20 -> w. w -> q_20. ~q_20.