Paco4000: That will be 70 euros.
Anna: 70 euros! Are you sure? This book costs 30 euros and this one 20 euros. The total should be 50!
Paco4000: There is no 50 percent discount on the second book.
Anna: How much is it then?
Paco4000: It costs 40 euros.
Anna: In that case, I don't want to buy it anymore!