If $\overline{\mathrm{a}}=3\overline{\mathrm{i}}+2\overline{\mathrm{j}}+\overline{\mathrm{k}}, \overline{\mathrm{b}}=\overline{\mathrm{i}}+\overline{\mathrm{j}}+2\overline{\mathrm{k}} \mathrm{and} \overline{\mathrm{c}}=\overline{\mathrm{i}}+3\overline{\mathrm{j}}+3\overline{\mathrm{k}}$ then the angle between $\overline{\mathrm{a}}$ and
the plane containing the face determined by $\overline{\mathrm{b}}$ and $\overline{\mathrm{c}}$ is