What can be inferred from the following premises in a single inference step (ignoring inferences that add new predicates or constants)? Richard is a cashier if and only if Robert is a soldier. Richard is a cashier if and only if Robert is a soldier.
If Richard were a cashier, then Robert is a soldier. If Richard were a cashier, then Robert is a soldier. If Robert were a soldier, then Richard is a cashier. If Robert were a soldier, then Richard is a cashier.