JEE Advanced 2015 · Paper 2, Physics question 3

The densities of two solid spheres $A$ and $B$ of the same radii $R$ vary with radial distance $r$ as $\rho_A(r)=k\left(\dfrac rR\right)$ and $\rho_B(r)=k\left(\dfrac rR\right)^5$, respectively, where $k$ is a constant. The moments of inertia of the individual spheres about axes passing through their centres are $I_A$ and $I_B$, respectively. If $\dfrac{I_B}{I_A}=\dfrac n{10}$, the value of $n$ is