Gravitation: JEE Main 2005 Physics question

A particle of mass $10$ $g$ is kept on the surface of a uniform sphere of mass $100$ $kg$ and radius $10$ $cm.$ Find the work to be done against the gravitational force between them to take the particle far away from the sphere (you may take $G$ $= 6.67 \times {10^{ - 11}}\,\,N{m^2}/k{g^2}$)