445. The teacher asked his twelfth‐grade students to name the most important invention. Among other things, they named the Internet, computers, smart phones, bicycles, and light bulbs. They named fishhooks, sewing machines, clocks, electric guitars, cat litter, and indoor plumbing. He asked, "Now, which is most important to you?" They voted. Smart phones were most important. He said, "Okay. I want all of you to promise me one thing. Promise not to use any bathrooms or water fountains for the next 24 hours. If you need a drink of water, go to the river. If you need to wash or bathe, go to the river. If you need to go to the bathroom, go to the river." The students groaned. The teacher asked, "Shall we vote again?" Peter said, "No. We got it. Indoor plumbing isn't sexy, but it's better than all the other inventions combined." The others murmured and nodded. 3.9