Extend the Story - Add a Room

Your heart rate soon returns to normal when he shows you the features of the "Drenchor6000" water gun. "And only for $14.95", he adds, grinning stupidly. Although you don't really need it, that price sounds quite reasonable to you for a water gun that lights up when it shoots and has a built in AM/FM radio. Digging in your pockets, you see what cash you can come up with. Your pockets contain: a $10 note, a $20 note, some gum and a movie ticket stub. You hand over the $20 note. "Uh, oh, I... don't have any change for you", the youth stammers. What do you do next?

Give him the $20 but ask him to come back when he has change.