Find the area of triangle by tangents at the point $P(at_1^2,2at_1)$ & $Q(at_2^2,2at_2)$ for the parabola $y^2=4ax$ .

Question

$\begin{array}{1 1}(a)\;\large\frac{1}{2}\normalsize \mid a^2(t_1-t_2)^3\mid\\(b)\;\large\frac{1}{4}\normalsize\mid a^2(t_1-t_2)^3\mid\\(c)\;\large\frac{1}{2}\normalsize\mid a^2(t_1+t_2)^3\mid\\(d)\;\large\frac{1}{2}\normalsize\mid a^2(t_2-t_1)^3\mid\end{array}$