Carl A. Boyle, a sales representative, was driving home when he saw a group of young children selling Kool-Aid on a corner in his neighborhood. They had posted the typical hand-scrawled sign over their stand: “Kool-Aid, 25 cents.”

Carl was intrigued. He pulled over to the curb. A young man approached and asked if he would like strawberry or grape Kool-Aid.

Carl placed his order and handed the boy a dollar. After much deliberation, the children determined he had some change coming and rifled through the cigar box until they finally came up with the correct amount. The boy returned with the change, then stood by the side of the car. He asked if Carl was finished drinking.

“Just about,” said Carl. “Why?”

“That’s the only cup we have,” answered the boy, “and we need it to stay in business.…