2. A barrel of oil weighs * * * 126 kg, and the weight after half is 7 1 kg. If 6 yuan per kilogram, how much can this barrel of oil sell?
3. A wire can be made into a rectangle with a length of 2 cm and a width of 8 cm. If this line is used to make two squares of the same size, how many centimeters should the sides of these two squares be?
The first warehouse stores 250 tons of grain, and the second warehouse stores 30 tons, which is more than twice that of the first warehouse. How many tons are stored in these two warehouses?
5. The school library has 12 bookshelves, with an average of 560 books per bookshelf. Now it has lent 1870 books to students and 480 books to teachers. How many books are there in the library?