Solution (source code)

= Solution

Substituting $J_m=\epsilon_{mij}M^{ij}/2$ and $K_i=M^{0i}$ yields
$$
\boxed{
[K_i,K_j]=-\epsilon_{ijk}J_k,\qquad
[J_i,K_j]=\epsilon_{ijk}K_k,\qquad
[J_i,J_j]=\epsilon_{ijk}J_k}.
$$