If the system of linear equations.
\( 8x + y + 4z = -2 \)
\( x + y + z = 0 \)
\( \lambda x - 3y = \mu \)
has infinitely many solutions, then the distance of the point \( \left(\lambda, \mu, -\dfrac{1}{2}\right) \) from the plane \( 8x + y + 4z = 0 \) is:
