The value of $\cos 12^{\large\circ}+\cos 84^{\large\circ}+\cos 156^{\circ}+\cos 132^{\large\circ}$ is

Question

$(a)\;\large\frac{1}{2}\qquad$$(b)\;1\qquad(c)\;-\large\frac{1}{2}$$\qquad(d)\;\large\frac{1}{8}$