Equation of normal for the parabola $y^2=4ax$ at point $(x_1,y_1)$ is

Question

$\begin{array}{1 1}(a)\;(y-y_1)=-\large\frac{y_1}{2a}\normalsize (x-x_1)\\(b)\;(y-2y_1)=-\large\frac{y_1}{a}\normalsize (x-2x_1)\\(c)\;(y-3y_1)=-\large\frac{y_1}{a}\normalsize (x-x_1)\\(d)\;(y-y_1)=-\large\frac{y_1}{2a^2}\normalsize (x-x_1)\end{array}$