For a construction site with 500 people, the fixed meal fee is about 10 yuan, and each person has three meals a day. If water, electricity and field rent are not included, his own expenses include 5,000 yuan per month for oil (if you buy an induction cooker, about 5,000 yuan can be ignored, but it needs 380 volts), labor (8 people * 1000 yuan, totaling 8,000 yuan per month) and billing. Lunch and dinner in 4 yuan, two meats and one dish, rice and soup (herbal tea and sugar water can be provided intermittently in summer) are served in unlimited quantities, and 80% of them are satisfied. It should guarantee a profit of 20%. That is, 25,000 to 30,000 yuan per month.