Problem 3.279

When a ball made of uniform magnetic is introduced into an external uniform magnetic field with induction $\mathbf{B}_{0}$, it gets uniformly magnetized. Find the magnetic induction $\mathbf{B}$ inside the ball with permeability $\mu$; recall that the magnetic field inside a uniformly mag netized ball is uniform and its strength is equal to $\mathbf{H}^{\prime}=-\mathbf{J} / \overrightarrow{3},$ where $J$ is the magnetization.