The article discusses how to find the best way to finance public infrastructure projects like the Tianjin Binhai New District Metro Z4 line in China. The researchers created a financial model using interval numbers to consider uncertain factors and help investors decide how much debt to take on. By analyzing different capital structures, they found that a 45% capital contribution ratio is the best plan for this project. This method can help investors make smarter decisions about how to fund projects and manage risks.