4.50%. There are many factors related to the purchasing desire of the consumer group, but relatively speaking, the profit of 15 yuan for a piece of Huajia vermicelli is still very considerable. In the catering industry, snacks account for a very large proportion, and a piece of Huajia vermicelli sells for 13 yuan. At that time, the profit was 4.5%, because it does not require a lot of manpower, the production method is relatively simple, and the store does not need to be large. Two people can open a henna powder store, so the profit is still considerable.