Physics HW. 2 questions multiple choice due after 3 hours ?

Density"

Q)Immeditaitly prior to a nuclear fission detonation, a pultonium spherical mass is compressed by high explosives in such a way that it briefly becomes a sphere with half the radius of the orginal sphere. As a result of the compression. the density of the sphere will:

1)douples
2)quadruples
3)increases by a factor of 8
4)decreases by a factor of 8

Q2)Length scale in physics
suppose  we model a hydrogen atom as a sphere with a radius of 0.53 A = 5.3 * 10^-11 m . what's the voulme of such an atom? recall that the volume of a sphere is V sphere = 4/3 pi r^3.

1)3.8 * 10^-15 m^3
2)1.2 * 10^-21 m^3
3)6.2 * 10^-31 m^3
4)2.8 *10^-42 m^3