RED: Buying three different books should apply 10% discount return 21.60 euros
GREEN: Buying three different books should apply 10% discount return 21.60 euros
REFACTOR: Buying three different books should apply 10% discount return 21.60 euros
RED: Buying four different books should apply 20% discount and return 25.60 euros
GREEN: Buying four different books should apply 20% discount and return 25.60 euros
REFACTOR: Buying four different books should apply 20% discount and return 25.60 euros
RED: Buying fice different books should apply 25% discount and return 30 euros
GREEN: Buying five different books should apply 25% discount and return 30 euros