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 an astronaut, then Robert is listening to a song. For all z, z is an astronaut if and only if z will listen to a song.
For all z, if z were an astronaut, then z is listening to a song can be inferred via the universal biconditional elimination rule. For all z, if z listens to a song, then z is an astronaut can be inferred via the universal biconditional elimination rule.