The latest project is to take a city of around half a million inhabitants and discovers exactly what raw materials 【S1】______ go into it and what go out. The aim is to find out how much of these raw materials could be provided whether a plant for 【S2】______ recycling waste were built just outside the city. This plant would recycle not only metal such as steel, lead but copper, but also 【S3】______ paper and rubber as well as. 【S4】______