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, x will not play squash. For all x, if x listens to a song, then x is playing squash. For all x, x will listen to a song if and only if x is an office clerk. For all x, if x listens to a song, then x is an office clerk.
For all x, x will not listen to a song can be inferred via the universal modus tollens rule. For all x, if x listens to a song, then x is an office clerk can be inferred via the universal biconditional elimination rule. For all x, if x were an office clerk, then x is listening to a song can be inferred via the universal biconditional elimination rule.