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 z, z will not listen to a song. Thomas is working if and only if Robert is listening to a song.
If Thomas works, then Robert is listening to a song can be inferred via the biconditional elimination rule. If Robert listens to a song, then Thomas is working can be inferred via the biconditional elimination rule.