Find the conditions for a co-normal point (h,k) of a parabola $y^2=4ax$

Question

$\begin{array}{1 1}(a)\;m_1+m_2+m_3=0\\(b)\;m_1m_2+m_2m_3+m_3m_1=\large\frac{2a-h}{a}\\(c)\;m_1m_2m_3=\large\frac{-k}{a}\\(d)\;\text{All of these}\end{array}$