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: If Michael works, then Sarah is rich. If Sarah were rich, then Michael is working. Sarah is rich if and only if Barbara is a cashier.
Michael is working if and only if Sarah is rich can be inferred via the biconditional introduction rule. Sarah is rich if and only if Michael is working can be inferred via the biconditional introduction rule. If Sarah were rich, then Barbara is a cashier can be inferred via the biconditional elimination rule. If Barbara were a cashier, then Sarah is rich can be inferred via the biconditional elimination rule.