Simplify $\frac{\cos 45^{\circ}}{\sec 30^{\circ}+cosec 30^{\circ}}$

$\frac{3 \sqrt{2}+\sqrt{6}}{8}$ $\frac{\sqrt{3}}{2 \sqrt{2}-2 \sqrt{6}}$ $\frac{3 \sqrt{2}-\sqrt{6}}{8}$ $\frac{\sqrt{3}}{2 \sqrt{6}-2 \sqrt{2}}$

$\frac{3 \sqrt{2}-\sqrt{6}}{8}$