A $2\, \text{g}$ object located in a region of a uniform electric field $\vec{E} = 300\, \text{N/C} \,\hat{i}$ carries a charge $Q$. The object is released from rest at $x = 0$ and has a kinetic energy of $0.12\, \text{J}$ at $x = 0.5\, \text{m}$. Then, $Q$ is