Making sure that encapsulation is not violated (i.e., instance variables must be private); design an inheritance hierarchy of classes Employee, CommissionEmployee, and BasePlusCommisionEmployee based on the following description. CommisionEmployee is an Employee. BasePlusCommissionEmployee is a CommisionEmployee. Note: BasePlusCommissionEmployee receives a base salary and commission. SSN is the Social Security Number. (a) (10 Points) Definition of class Employee Instance variables: . firstName that holds the first name of employee (string) . lastName that holds the last name of employee (string) socialSecurityNumber that holds the social security number of employee (string)