Consider the following structure for company W. It has a CEO, 2 VP for marketing and manufacturing. The Manufacturing VP manages the Product Manager and the Shipment Manager. The Marketing VP manages the Sales Manager and the Marketing Manager. Each of the managers at the 3rd level of management hierarchy manages a number of Employees. The cost of an individual employee is simply his salary. The cost of an employee who heads a department is his salary plus those of all his subordinates. We would like a single interface that will produce the salary totals correctly whether the employee has subordinates or not. Show the class diagram that captures the requirement specified above.