Many city ordinances have a requirement that buildings be surrounded by a certain amount of empty space for sunlight and fresh air. Apartment buildings-- begin residences and in particular multiple dwelling, usually have higher requirements than commercial or single residence properties. These requirements are often based upon square footage, number of occupants, etc. Assume the existence of a class Building with a method getRequiredEmptySpace that returns the amount of empty space (as an integer representing square feet) for the building. Asume further, a subclass, ApartmentBuilding, with two integer instance variables: totalUnits representing the number of apartments in the building and maxOccupantsPerUnit, represents the maximum number of people allowed in each unit, by law. Override getRequiredEmptySpace in ApartmentBuilding to reflect the fact that apartment buildings require an addition square foot of empty space around it for each potential person living in the building.