Two particles each of mass m are placed at points P and Q . R is the mid point of PQ = l . The gravitational force on the third particle of mass m placed at point s on the perpendicular bisector of PQ at a distance l from R is ?
A)Gm2/l2
B)16Gm2/5l2
C)16Gm2/5(5)1/2l22
D)4(2)1/2Gm2/5l2