Given the abstract class, Rentable Dwelling, containing:.
a. a (private) double instance variable, rent Per Unit.
b. a constructor accepting a double used to initialize rent Per Unit.
c. a method, get Rent Per Unit that returns the value of rent Per Unit.
d. an abstract method get Rent all Income that returns a double.
Write a (non-abstract) subclass, Apartment House, containing:.
a. an int instance variable number Of Apartments.
b. a constructor accepting a double, passed to the superclass constructor, and an int used to initialize number Of Apartments.
c. the method get Rent alI Income calculated as the product of number Of Apartments and the rent per unit. Get Rent all Income returns a double.