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: If Robert were a taxi driver, then William is not playing tennis. For all z, z will listen to a song if and only if z is a taxi driver. William is playing tennis.
Robert is not a taxi driver can be inferred via the modus tollens rule. For all z, if z listens to a song, then z is a taxi driver can be inferred via the universal biconditional elimination rule. For all z, if z were a taxi driver, then z is listening to a song can be inferred via the universal biconditional elimination rule.