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: James is not a janitor. If it rains, then James is a janitor. It is sunny if and only if Richard is fast. Richard is not fast.
It is not raining can be inferred via the modus tollens rule. James is not a janitor and Richard is not fast can be inferred via the conjunction rule. Richard is not fast and James is not a janitor can be inferred via the conjunction rule. If it is sunny, then Richard is fast can be inferred via the biconditional elimination rule. If Richard were fast, then it is sunny can be inferred via the biconditional elimination rule. It is not sunny can be inferred via the biconditional elimination rule.