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_12 for which x_12 will listen to a song or x_12 is sad. For all x_12, if x_12 listens to a song, then x_12 is reading a book. For all x_12, if x_12 were sad, then x_12 is climbing a mountain. For all x_12, x_12 will cook. For all x_12, if x_12 climbs a mountain, then x_12 is reading a book.
For all x_12, if x_12 were sad, then x_12 is reading a book can be inferred via the universal transitivity rule.