If $ x= \large\frac{\sqrt 3 +1}{\sqrt 3 -1} $ and $y=\large\frac{ \sqrt 3 -1}{\sqrt 3 +1}$ then the value of $(x^2+y^2)$ is

Question

$\begin{array}{1 1} 10 \\ 13 \\ 14 \\ 15 \end{array} $