Find the length of lactus rectum and end points of lactus rectum for a ellipse $\large\frac{x^2}{a^2}+\frac{y^2}{b^2}$$=1$?

Question

$\begin{array}{1 1}(a)\;\large\frac{2b^2}{a}\\(b)\;\large\frac{b^2}{a}\\(c)\;\large\frac{4b^2}{a}\\(d)\;\large\frac{2a^2}{b}\end{array}$