Two discs rotating about their respective axis of rotation with angular speeds $2 \text{ rads}^{-1}$ and $5 \text{ rads}^{-1}$ are brought into contact such that their axes of rotation coincide. Now, the angular speed of the system becomes $4 \text{ rads}^{-1}$. If the moment of inertia of the second disc is $1 \times 10^{-3} \text{ kg m}^2$, then the moment of inertia of the first disc (in $\text{kg m}^2$) is}