The area (in sq. units) of the region $\{ (x,y) : y^2 \geq 2x$ and $x^2 + y^2 \leq 4x, \; x \geq 0, \; y \geq 0 \}$ is :

Question

( A ) $\frac{\pi}{2} - \frac{2 \sqrt{2}}{3}$
( B ) $\pi - \frac{4}{3}$
( C ) $\pi - \frac{8}{3}$
( D ) $\pi - \frac{4 \sqrt{2}}{3}$