Two block of masses $$3\ kg$$ and $$6\ kg$$ rest on a horizontal frictionless surface. The $$3\ kg$$ block is attached to a spring with a force constant $$k=900\ N/m$$ which is compressed $$2\ m$$ initially from its equilibrium position. When $$3\ kg$$ mass is released, it strikes the $$6\ kg$$ mass and the two stick together in an inelastic collision.
The velocities of a particle executing S.H.M. are $$30\ cm/s$$ and $$16\ cm/s$$ when its displacements are $$8\ cm$$ and $$15\ cm$$ from the equilibrium position. Then its amplitude of oscillation in $$cm$$ is