Two point charges $\;q_{1}=q_{2}=2\;\mu C\;$ are fixed at $\;x_{1}= +3m \;and\;x_{2}=-3m\;$ as shown in figure . A third particle of mass 1g and charge $\;q_{3}=-4\;\mu C\;$ are released from rest at $\;y=4m \;$. Find the speed of the particle as it reaches the origin .