For example, the cost problem often mentioned in economics is often seen in milk and coke. Cost is a problem that everyone who develops the economy will consider. After all, cost is an indispensable expenditure, and it is impossible to develop the economy without cost. In milk and cola, milk is usually packed in cartons. Coke is usually sold in plastic bottles. It can be seen from this that although the two drinks are often drunk in daily life, the packaging used is really different. On the one hand, milk is basically white, and people don't need to see its color. Besides, it's cheaper to use cartons. Coke is a kind of soda, which stimulates people's taste buds, so using transparent plastic bottles can make people see its color and arouse their appetite. And the composition of plastic bottles is really not high. And from an economic point of view, when you invent and research a product, you should not only consider the cost, but also consider whether the user is convenient. As a drink that can be drunk everywhere, cola is actually easy to carry, so it is designed as a bottle, which can be put in a bag at will, making it more convenient to drink. If coke is designed to be packed in cartons, it will actually take up a lot of space, and the weight of cartons themselves will be heavier than that of plastic bottles. Therefore, it is convenient for consumers to sell bottled coke, and it will also make consumers more comfortable to use. In addition, the storage mode is also a point that needs to be considered in economics. After all, selling this kind of beverage generally considers the storage method. Milk is packed in cartons, which is convenient for cold storage, but if coke is packed in cartons, it can be refrigerated, but it is not as easy to freeze as plastic bottles. Coke is delicious only if it is chilled.