Three charges $-q_{1,}+q_{2}$ and $-q_{3}$ are placed as shown in figure. The $x$ component of the force on $-q_{1}$ is proportional to
(a) $\frac{q_{2}}{b^{2}}-\frac{q_{3}}{a^{2}} \sin \theta$
(b) $\frac{q_{2}}{b^{2}}-\frac{q_{3}}{a^{2}} \cos \theta$
(c) $\frac{q_{2}}{b^{2}}+\frac{q_{3}}{a^{2}} \sin \theta$
(d) $\frac{q_{2}}{b^{2}}+\frac{q_{3}}{d^{2}} \cos \theta$