Let the directrix of the parabola \( P: y^{2} = 8x \), cut x-axis at the point \( A \). Let \( B(\alpha, \beta),\ \alpha > 1 \), be a point on \( P \) such that the slope of \( AB \) is \( \frac{3}{5} \). If \( BC \) is a focal chord of \( P \), then six times the area of \( \triangle ABC \) is:
