The area of the region lying above \(x\)-axis, and included between the circle \(x^{2}+y^{2}=2 a x \&\) the parabola \(y^{2}=a x\), \(a>0\) is
(A) \(8 \pi a^{2}\)
(B) \(\mathrm{a}^{2}\left(\frac{\pi}{4}-\frac{2}{3}\right)\)
(C) \(\frac{16 \pi a^{2}}{9}\)
(D) \(\pi\left(\frac{27}{8}+3 a^{2}\right)\)
