Q42

Q42. A charge configuration is shown in figure. What is the potential at a point P at a distance r on the axis, as shown assuming r >> a ?
                 
               

       $$\begin{gathered} \left(\mathrm{a}\right) \frac{\mathrm{q}}{4{\mathrm{\pi \epsilon }}_0}\left(\frac{2\mathrm{a}}{{\mathrm{r}}^2}+\frac{1}{\mathrm{r}}\right) \left(\mathrm{b}\right) \frac{\mathrm{q}}{4{\mathrm{\pi \epsilon }}_0}\left(\frac{2\mathrm{a}}{\mathrm{r}}+\frac{1}{{\mathrm{r}}^2}\right) \\ \left(\mathrm{c}\right) \frac{\mathrm{q}}{4{\mathrm{\pi \epsilon }}_0}\left(\frac{\mathrm{a}}{{\mathrm{r}}^2}+\frac{1}{\mathrm{r}}\right) \left(\mathrm{d}\right) \frac{\mathrm{q}}{4{\mathrm{\pi \epsilon }}_0}\left(\frac{\mathrm{a}}{{\mathrm{r}}^2}+\frac{2}{\mathrm{r}}\right) \end{gathered}$$