KEAM 2014 Physics and Chemistry Paper

Two discs rotating about their respective axis of rotation with angular speeds 2 rads−1 and 5 rads−1 are brought into contact such that their axes of rotation coincide. Now, the angular speed of the system becomes 4 rads−1. If the moment of inertia of the second disc is 1×10−3kg m2, then the moment of inertia of the first disc (in kg m2) is