Duvida extends

Section 1: Declarations, Initialization and Scoping &gt Objective 1.2 &gt Question 3 

Given: 

1. abstract class Color {
2.   protected abstract String getRGB(); 
3. }
4. 
5. public class Blue extends Color {
6.   // insert code here
7. } 

And four declarations: 

     public String getRGB() { return "blue"; }
     String getRGB() { return "blue"; } 
     private String getRGB() { return "blue"; }
     protected String getRGB() { return "blue"; }

How many, inserted independently at line 6, will compile?