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: There is at least one x_9 for which x_9 will not listen to a song. For all x_9, x_9 is a doctor. For all x_9, x_9 is a doctor if and only if x_9 will listen to a song.
Since the premises are contradictory, we can infer anything from them.