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 a writer. For all x_9, x_9 will play squash if and only if x_9 will listen to a song. For all x_9, x_9 will play squash or x_9 is bored. For all x_9, x_9 is not a writer.
For all x_9, x_9 will not listen to a song can be inferred via the universal modus tollens rule. For all x_9, if x_9 plays squash, then x_9 is listening to a song can be inferred via the universal biconditional elimination rule. For all x_9, if x_9 listens to a song, then x_9 is playing squash can be inferred via the universal biconditional elimination rule.