If the hemisphere has radius 2, then the sphere will have radius 1. Solving for the formula of a sphere, we get 4/3 pi, which simplifies to about 4.2

HiylinLink, your answer is wrong probably becuase you didn't read the question carefully

The sphere is inscribed in the hemisphere, so the sphere doesn't have radius 2, it has radius 1. If the sphere has radius 2, then your answer is correct. But since it has radius 1, the answer is 4.2