Electrostatics

The distance between charges \(+q\) and \(-q\) is \(2 l\) and between \(+2 q\) and \(-2 q\) is \(4 l\). The electrostatic potential at point \(P\) at a distance \(r\) from center \(O\) is \(-\alpha\left[\frac{q l}{r^2}\right] \times 10^9 \mathrm{~V}\), where the value of \(\alpha\) is __________. (Use \(\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \mathrm{~Nm}^2 \mathrm{C}^{-2}\))