Acylindrical metal pipe has a diameter of 20 millimeters and a height of 21 millimeters. a cylindrical hole cut out of the center has a radius of 6 millimeters.

which expressions represent the volume of metal needed, in cubic millimeters, to make the pipe? check all that apply.

21π(10)2 – 21π(6)2
π(20)2(21) – π(6)2
2,100π – 756π
7,644π
1,344

answer is choice 1 and 3.