If the position vector of one end A of a diameter AB of the sphere  $\overline{\mathrm{r}}.\left|\overline{\mathrm{r}}-(2\overline{\mathrm{i}}-\overline{\mathrm{j}}+4\overline{\mathrm{k}}) \right|= 5$ is $\left(\overline{\mathrm{i}}+2\overline{\mathrm{j}}-\overline{\mathrm{k}}\right)$ , the position vector of B is