$A$ luminous point object $O$ is placed at a distance $2R$ from the spherical boundary separating two transparent media of refractive indices $n_1$ and $n_2$ as shown,where $R$ is the radius of curvature of the spherical surface. If $n_1 = \frac{4}{3}$,$n_2 = \frac{3}{2}$ and $R = 10 \text{ cm}$,the image is obtained at a distance from $P$ equal to:

• A
  $30 \text{ cm}$ in the rarer medium
• B
  $30 \text{ cm}$ in the denser medium
• C
  $18 \text{ cm}$ in the rarer medium
• D
  $18 \text{ cm}$ in the denser medium