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 Barbara were an electrician, then Sarah is a cashier. If Barbara were an electrician, then Sarah is a cashier. If Sarah were a cashier, then Barbara is an electrician.
Barbara is an electrician if and only if Sarah is a cashier can be inferred via the biconditional introduction rule. Barbara is an electrician if and only if Sarah is a cashier can be inferred via the biconditional introduction rule. Sarah is a cashier if and only if Barbara is an electrician can be inferred via the biconditional introduction rule. Sarah is a cashier if and only if Barbara is an electrician can be inferred via the biconditional introduction rule.