The value of $\cos(45^{\circ}-A)\cos(45^{\circ}-B)-\sin(45^{\circ}-A)\sin(45^{\circ}-B)$ is equal to

Question

$\begin{array}{1 1}(a)\;\sin(A+B)&(b)\;\cos(A+B)\\(c)\;\sin(A-B)&(d)\;\cos(A-B)\end{array}$