SOLVED: It’s possible to include the functionality of the payroll application (Figs. 10.4–10.9) in the accounts payable application without modifying Employee sub classes Salaried Employee, Hourly Employee, Commission Employee or Base Plus Commission-Employee. To do so, you can modify class Employee (Fig. 10.4) to implement interface Payable and declare method get Payment Amount to invoke method earnings. Method get Payment Amount would then be inherited by the sub classes in the Employee hierar