1. Create an interface named Payable which contains one method called pay(). This method takes one double argument and return a double. Define a class named Invoice which implements the interface Payable. Inside of the Invoice class, overrides the pay() method, returns the double that passes in the double argument.

2. Write the clause needed to identify a method as one that may throw a NegativeException.

3. The superclass BankAccount contains:

a constructor that accepts a double corresponding to the balance of the account

a toString method that returns 'account has balance of YYY ' where YYY is the balance of the account

Write a class definition for the subclass CheckingAccountcontaining:

a constructor accepting a double which is used as a parameterto the superclass constructor

a toString method that returns 'Checking account has balance of YYY'. This method must use the toString method of its superclass.