If $(a, 0) ; a>0$ is the point where the curve $y=\sin 2 x-\sqrt{3} \sin x$ cuts the $X$ -axis first, $A$ is the area bounded by this part of the curve, the origin and the positive $X$ -axis, then
(a) $4 A+8 \cos a=7$
(b) $4 A+8 \sin a=7$
(c) $4 A-8 \sin a=7$
(d) $4 A-8 \cos a=7$