Define a public class Whisperer that provides a single class method named whisper. whisper should accept a single Person instance and return a String. If the person is:

• a Student you should return the result of calling hey()
• a Staff you should return the result of calling help()
• a Professor you should return the result of calling hello()
• otherwise return null.

You will need to downcast the passed Person appropriately in order to access and call the methods as described above.