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, if z works, then z is a janitor. Richard is a janitor if and only if it is sunny.
If Richard were a janitor, then it is sunny can be inferred via the biconditional elimination rule. If it is sunny, then Richard is a janitor can be inferred via the biconditional elimination rule.