The question is fishing for "balanced force".
But the description in the question is terrible.
Answer:
kinetic energy
Explanation:
0.29D
Given that
F = G M m / r2
F = GM(6m) / (D-r)2
G Mm/r2 = GM(6m) / (D-r)2
1/r2 = 6 / (D-r)2
r = D / (Ö6 + 1)
r = 0.29 D
See diagram in attached file
C) 20
Happy Halloween LOL
Using law of conservation of momentum