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_14, if x_14 were a sailor, then x_14 is listening to a song. Robert is a sailor or Sarah is a police officer. If Sarah were a police officer, then Robert is listening to a song. If Robert listens to a song, then Mary is happy.
Nothing can be inferred from these premises.