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: Joseph is playing squash if and only if Richard is excited. If Sarah listens to a song, then Joseph is playing squash. David is fast. If Richard were excited, then James is a cashier. If James were a cashier, then David is not fast.
James is not a cashier can be inferred via the modus tollens rule. If Richard were excited, then David is not fast can be inferred via the transitivity rule. If Joseph plays squash, then Richard is excited can be inferred via the biconditional elimination rule. If Richard were excited, then Joseph is playing squash can be inferred via the biconditional elimination rule.