(i) Define instance variables for the customer ID (a String) and the customer name (a String).
Also define a constructor for the Customer class, which accepts the customer ID , name and phone number and name as parameters.
(iii) Define accessors for the customer ID and name.
(vii) Define an abstract method public abstract void completeSale (double price), which the customer subclasses will have to override later on.
(iv) Define a method public void print(), which prints a summary of the details (instance variables) for the customer to the screen.