Elmhurst Corporation is considering changes to its responsibility accounting system. Which of the following statements​ is/are correct for a responsibility accounting​ system? I. In a cost​ center, managers are responsible for controlling costs but not revenue. II. The idea behind responsibility accounting is that a manager should be held responsible for those items that the manager can control to a significant extent. III. To be​ effective, a good responsibility accounting system must help managers to plan and to control. IV. Costs that are allocated to a responsibility center are normally controllable by the responsibility center manager.