When people enter their telephone numbers into a form they use many different formats. Some examples are: 

   (444) 999-1234
   4449991234
   444.999.1234
In the PhoneNumbers class below, complete the cleanNumber method. It takes a string and extracts the numeric digits from the string. If there are exactly 10 numeric digits, the number is reformatted: (###) ###-#### and returned. If there are any other number of digits, the string "Error" is returned.

Hint: Use the Character.isDigit method to check whether a character is a digit.