Let a line having direction ratios \( 1, -4, 2 \) intersect the lines \( \dfrac{x-7}{3} = \dfrac{y-1}{-1} = \dfrac{z+2}{1} \) and \( \dfrac{x}{2} = \dfrac{y-7}{3} = \dfrac{z}{1} \) at the point A and B. Then \( (AB)^2 \) is equal to ______________.
