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 Thomas were a taxi driver, then Thomas is a janitor. For all z_2, if z_2 were a janitor, then z_2 is a taxi driver. If Jennifer were an astronaut, then Thomas is a janitor. Thomas is a taxi driver if and only if John is listening to a song. John is not listening to a song.
If Thomas were a taxi driver, then John is listening to a song can be inferred via the biconditional elimination rule. If John listens to a song, then Thomas is a taxi driver can be inferred via the biconditional elimination rule. Thomas is not a taxi driver can be inferred via the biconditional elimination rule.