Build a Ruby class for a Building that:
- Initializes with a name, address, number of floors, and number of tenants
- The name and number of tenants should be readable and writeable
- The address should be readable
- The number of floors should not be readable or writeable
- The class should keep track of all buildings that are created
- The class should tell the average number of tenants in a building
- A building should have a placard method that returns the name and address of the building
- A building should have a method returns the average number of tenants per floor
Then:
Make objects for the three buildings on this corner. Use a Fermi estimate for the number of tenants.