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: For all x_9, x_9 is a doctor or x_9 will not listen to a song. For all x_9, if x_9 were happy, then x_9 is a doctor. For all x_9, x_9 is bored. For all x_9, x_9 will listen to a song or x_9 is happy.
For all x_9, if x_9 listens to a song, then x_9 is a doctor can be inferred via the universal rewriting rule.