giving brainiest and 85 points!

Answer:
12 560 cubic feet
Step-by-step explanation:
radius of circular cross section = 20ft/2 = 10ft
Area of circular cross section = πr²
= 3.14 x 10 x 10
= 314 square feet
Volume of cylindrical tank = 314 ft² x 40ft
= 12 560 ft³