A solid sphere of radius $$R$$ gravitationally attracts a particle placed at $$3R$$ from its centre with a force $$F_1$$. Now a spherical cavity of radius $$\frac{R}{2}$$ is made in the sphere (as shown in figure) and the force becomes $$F_2$$. The value of $$F_1 : F_2$$ is:

A

41 : 50

B

50 : 41

C

25 : 36

D

36 : 25