The distance $x_{2}$ from point $b$ where the field is maximum, will be

(A) $\frac{\ell}{\left(\frac{\varepsilon+x_{1}}{x_{1}}\right)^{\frac{2}{3}}-1}$

(B) $\frac{\ell}{\left(\frac{\ell+x_{1}}{x_{1}}\right)^{\frac{1}{3}}-1}$

(C) $\frac{\varepsilon}{\left(\frac{r+2 x_{1}}{x_{1}}\right)^{\frac{2}{3}}-1}$

(D) $\frac{\ell}{\left(\frac{\ell+2 x_{1}}{x_{1}}\right)^{\frac{1}{3}}}$