https://drive.google.com/file/d/0B7Hi5tWF6BDbRXhDenZNR2NDYngxMFhZaEh4ZGpMendpbXdF/view?usp=sharing
This object is known as the frustum of a right circular cone .
The volume is given by :
pi * height ( r2^2 + r1r2 + r1^2 ) / 3
The height is not given but it is the leg of a right triangle with the other leg = 12 - 8 = 4
And the hypotenuse = l = 10
So the height is sqrt (10^2 - 4^2) = sqrt (100 - 16) = sqrt (84) = 2sqrt (21)
So the volume is
pi * 2sqrt (21) * [ 12^2 + 8*12 + 8^2 ] / 3 =
pi * 2sqrt (21) * [ 144 + 96 + 64] / 3 =
pi * 2sqrt (21) * [ 304] / 3 =
[ (608/3) * sqrt (21) pi ] units ^3