The angle between the straight lines, whose direction cosines are given by the equations \( 2l + 2m - n = 0 \) and \( mn + nl + lm = 0 \), is:
\( \cos^{-1}\!\left(\frac{8}{9}\right) \)
\( \pi - \cos^{-1}\!\left(\frac{4}{9}\right) \)
\( \frac{\pi}{2} \)
\( \frac{\pi}{3} \)