Create the classes in the following inheritance hierarchy. An Employee should have a first

name, last name and ID number. In addition, the SalariedEmployee should have a weekly

salary; an HourlyEmployee should have a wage and a number of hours worked; a

CommissionEmployee should have a commission rate and gross sales; and a

BaseCommissionEmployee should have a base salary. Each class should have an appropriate

constructor, setters and getters. Each Employee should have an earning$()$ and toString$()$

methods. Also make Employee comparable. The compareTo method compares between the

employees based on earnings.