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, if x_9 listens to a song, then x_9 is playing squash. For all x_9, x_9 will listen to a song or x_9 will not write a letter. For all x_9, if x_9 plays squash, then x_9 is reading a book. For all x_9, if x_9 reads a book, then x_9 is working.
For all x_9, if x_9 listens to a song, then x_9 is reading a book can be inferred via the universal transitivity rule. For all x_9, if x_9 plays squash, then x_9 is working can be inferred via the universal transitivity rule. For all x_9, if x_9 writes a letter, then x_9 is listening to a song can be inferred via the universal rewriting rule.