How do you get to 104 using the numbers 3,2,5 and 8 adding, diving, multiplying or subtracting once

Volume of a cylinder = the area of the base x height of the cylinder
Area of base = r^2
A = 6^2()
A = 36
V = 36 x 12
V = 432

5 cylinders = 5V

5V = 5 x (432)
5V = 2160

Final Alex needs to buy 2160 or 6785.84 cubic feet worth of compressed air to fill all of the cylindrical tanks.