A ring has a total mass M but not uniformly distributed over its circumference . The radius of ring is R. A Point mass m is placed at the center of the ring. Work done in taking away this point mass from center to infinity is

Question

$$(a)\;\frac{-GMm}{R} \quad (b)\;\frac{GMm}{R} \quad (c)\;\frac{GMm}{2R} \quad (d)\;can\;not\;be\;calculated$$