A parabola $x=y^2$ with $0 \leq x \leq 1$ is shown in the figure. The volume of the solid of rotation obtained by rotating the shaded area by $360^{\circ}$ around x-axis is
1. $\frac{\pi}{4} \\$
2. $\frac{\pi}{2} \\$
3. ${\pi} \\$
4. $2 \pi$