A cubical volume is bounded by the surfaces $x=0, x=a, y=0, y=a, z=0, z=a$. The electric field in the region is given by $\dot{E}=E_0 x \hat{i}$. Where $E_0=4 \times 10^4 \mathrm{NC}^{-1} \mathrm{~m}^{-1}$. If $a=2 \mathrm{~cm}$, the char contained in the cubical volume is $\mathrm{Q} \times 10^{-14} \mathrm{C}$. The value of Q is $\_\_\_\_$ . Take $\epsilon_0=9 \times 10^{-12} \mathrm{C}^2 / \mathrm{Nm}^2$ )