Someone explain how to get the answer and what the answer is you

The volume of a cylinder is

V=hpr^2 in this case h=40, r=20/2=10, and we will approximate pi as 3.14 so:

V=40(3.14)(10^2)

V=12560 ft^3

First step is to get rid of the square root. remember that a square root is the same as raising to the (1/2) power. see below: multiply exponents per exponent rules to get: remember you subtract exponents from the denominator and add exponents in the numerator so: simplify further: so a is the correct choice. if you don't understand this google exponent rules and it will you understand. look at the image results.