A charge $+q$ is fixed at each of the point$x=x_0,x=3x_0,x=5x_0 \dots \dots \dots$ to $\propto$ on the $X$ -axis and a charge $-q$ is fixed at each of the points of the points $x=2x_0,x=4x_0,x=6x_0\dots \dots \dots .$ to $\propto$, Here $x_0$ is a positive constant. Take the electric potential at a point due to a charge $Q$ at a distance $r$ from it to be $\frac{1}{4\pi {\epsilon }_0}\frac{Q}{r}.$ Then, the potential at the origin due to the above system of the charges is -