$\lim\limits_{x\to \large\frac{\pi}{4}}\large\frac{\cos x-\sin x}{(\Large\frac{\pi}{4}-\normalsize x)(\large\cos x+\sin x)}$ is

Question

$(a)\;0\qquad(b)\;1\qquad(c)\;-1\qquad(d)\;None\;of\;these$