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: It is overcast if and only if Elisabeth is cooking. If Barbara listens to a song, then Elisabeth is cooking. If Karen were a janitor, then Barbara is listening to a song.
If Karen were a janitor, then Elisabeth is cooking can be inferred via the transitivity rule. If it is overcast, then Elisabeth is cooking can be inferred via the biconditional elimination rule. If Elisabeth cooks, then it is overcast can be inferred via the biconditional elimination rule.