One end of a thin uniform rod of length $2L$ and mass $M_1$ is rivetted to the centre of a uniform circular disc of radius $\text{'}r\text{'}$ and mass $M_2$ so that both are coplanar.  The centre of mass of the combination from the centre of the disc is (Assume that the point of attachment is at the origin)

• A

  $\frac{\text{L}\left({\text{M}}_{\text{1}}+{\text{M}}_{\text{2}}\right)}{{\text{2M}}_{\text{1}}}$

• B

  $\frac{M_{1}L}{M_1+M_2}$

• C

  $\frac{\text{2}\left({\text{M}}_{\text{1}}+{\text{M}}_{\text{2}}\right)}{{\text{LM}}_{\text{1}}}$

• D

  $\frac{{\text{2LM}}_{\text{1}}}{\left({\text{M}}_{\text{1}}+{\text{M}}_{\text{2}}\right)}$