There is no dark blue ball in the box. 
There are $20$ balls of the same size in a box.  Lucas says: "Half of them are red."  Peter says: "The number of red balls is $5$ times that of green balls."  Claire says: "There are three colors of balls in the box: red, light blue, and green."  How many dark blue balls are there in the box? 
1. $$0$$ 
2. $$2$$ 
3. $$6$$ 
4. $$8$$ 
5. $$10$$ 