Rotational Motion

A force of $(2 \hat{\mathbf{i}}+3 \hat{\mathbf{j}}+4 \hat{\mathbf{k}}) \mathrm{N}$ acts on a particle whose position vector with respect to the origin of the coordinate system is $(6 \hat{\mathbf{i}}+b \hat{\mathbf{j}}+12 \hat{\mathbf{k}}) \mathrm{m}$. If the angular momentum of the body is constant, the value of $b$ is