Two planets, each of mass $$M$$ and radius $$R$$, are positioned at rest in space with their centres a distance $$4R$$ apart. You wish to fire a projectile from the surface of one planet to the other. The minimum initial speed for which this may be possible is

A

$$\sqrt{\frac{2GM}{5R}}$$

B

$$\sqrt{\frac{2GM}{3R}}$$

C

$$\sqrt{\frac{4GM}{3R}}$$

D

$$\sqrt{\frac{3GM}{2R}}$$