Answer
$2 \pi$
Work Step by Step
Area $=R^2\pi- r^2 \pi=\pi (4-4x)$
We integrate the integral to calculate the volume as follows:
$V= \pi \times \int_{0}^{1} (4-4x) dx$
Now, $V= \pi [4x-2x^2]_{0}^{1}$
or, $= \pi (4-2-0+0)$
or, $=2 \pi$