You get half a catty if you buy a catty. This promotion method is too awesome. The price of merchants is half a catty from 20 yuan, which means that 20 yuan is half a catty, which captures the psychology of customers who are greedy for cheap. Every customer will choose 20 yuan to buy half a catty instead of 10 yuan half a catty. As a result, merchants sold more goods.

If the merchant directly sells a kilo of 14 yuan, then the customer will buy a kilo of flowers 14 yuan instead of a kilo and a half of 20 yuan, and the merchant will sell less.