$\begin{array}{1 1}(A)\;30^{\circ} \: or \: 150^{\circ} \\(B)\; 45^{\circ} \: or \: 315^{\circ} \\(C)\; 60^{\circ} \: or \: 120^{\circ} \\(D)\;0^{\circ} \end{array} $