Let one root of the quadratic equation in \( x \): \( (k^{2}-15k+27)x^{2}+9(k-1)x+18=0 \) be twice the other. Then the length of the latus rectum of the parabola \( y^{2}=6kx \) is equal to:
\( 4 \)
\( 6 \)
\( 8 \)
\( 12 \)