The area (in sq units) of the region $\left\{(x, y): y^{2} \geq 2 x\right.$ and $\left.x^{2}+y^{2} \leq 4 x, x \geq 0, y \geq 0\right\}$ is $\quad$
(a) $\pi-\frac{4}{3}$
(b) $\pi-\frac{8}{3}$
(c) $\pi-\frac{4 \sqrt{2}}{3}$
(d) $\frac{\pi}{2}-\frac{2 \sqrt{2}}{3}$