2) challenge: to avoid theft, the store owners don't want to let too much money collect in the machine so they take all the money out when they think the machine has about $ 50 in it. the tricky part is that the store owners can't tell how much money is actually in the machine without opening it up, so they choose when to remove the money by judging how many candies are left in the machine. about how full should the machine look when they take the money out? how do you know?