Three urns \( A \), \( B \) and \( C \) contain \( 4 \) red, \( 6 \) black; \( 5 \) red, \( 5 \) black; and \( \lambda \) red, \( 4 \) black balls respectively. One of the urns is selected at random and a ball is drawn. If the ball drawn is red and the probability that is drawn from urn \( C \) is \( 0.4 \) then the square of the length of the side of the largest equilateral triangle, inscribed in the parabola \( y^2=\lambda x \) with one vertex at the vertex of the parabola, is:
