Two hypothetical planets of masses m1 and m2 are at rest when they are infinite distance apart. Because of the gravitational force they move towards each other along the line joining their centers. What are their speeds when their separation is 'd'? (Speed of m is vz and that of mz is vz) (A) v1 = v2 2G vi = m2 (d(m +mg) V2 = m1 V (C) v1 2G V1 = mi (d(m+ma) V2 = m2. (D) 2G