$A$ uniform circular disc of radius $a$ is taken. $A$ circular portion of radius $b$ has been removed from it as shown in the figure. If the centre of the hole is at a distance $c$ from the centre of the disc,the distance $x_2$ of the centre of mass of the remaining part from the initial centre of mass $O$ is given by

• A
  $\frac{{\pi {b^2}}}{{\left( {{a^2} - {b^2}} \right)}}$
• B
  $\frac{{ - c{b^2}}}{{\left( {{a^2} - {b^2}} \right)}}$
• C
  $\frac{{\pi {c^2}}}{{\left( {{a^2} - {b^2}} \right)}}$
• D
  $\frac{{\pi {a^2}}}{{\left( {{c^2} - {b^2}} \right)}}$