How it works
A business makes or sells something people want, again and again. It works like a circle: people want something, the business makes it, people pay, and the business uses some of those coins to make more.
Leo's cart needs start-up costs, paid once before the first sale: a used cart (10 coins), a sign (2 coins) and a jug and ladle (4 coins).
Each cup also has a running cost, because it comes back with every cup: a lemon, sugar and a paper cup, 1 coin in all.
A good price is more than the running cost. A cup sold for 3 coins pays for the next cup and leaves 2 coins over.