If the line \( 3x - 2y + 12 = 0 \) intersects the parabola \( 4y = 3x^2 \) at the points \( A \) and \( B \), then at the vertex of the parabola, the line segment \( AB \) subtends an angle equal to:
\( \tan^{-1}\!\left( \frac{9}{7} \right) \)
\( \tan^{-1}\!\left( \frac{4}{5} \right) \)
\( \tan^{-1}\!\left( \frac{11}{9} \right) \)
\( \frac{\pi}{2} - \tan^{-1}\!\left( \frac{3}{2} \right) \)