My friend Martin went to La Paz, Bolivia, for a business conference. While on a mid-morning stroll, he saw an apple vendor sitting on a box, behind a small pile of delicious-looking apples. Martin figured his friends at the conference would enjoy an apple, too, so he told the vendor he’d buy all her apples. She flat-out refused to sell to him. He tried to cajole and otherwise persuade her, to no avail. “Senor, I can’t let you buy all my apples. If I sell out now I won’t have anything to do for the rest of the day.”