A uniform ring of mass $M$ and radius $R$ is placed directly above a uniform sphere of mass $8M$ and of radius $R$. The center of the ring is at a distance of $d= \sqrt 3 R$ from the center of the sphere. The gravitational attraction between the sphere and ring is

Question

$$(a)\;\frac{8GM^2}{R^2} \quad (b)\;\frac{2GM^2}{\sqrt R^2} \quad (c)\;\frac{3GM^2}{2R^2} \quad (d)\;\frac{\sqrt 3 GM^2}{R^2}$$

Comments

why is the converse not true?
find the electric field of the sphere and then multiply by mass of ring?