Solve this:

Q. 72. An infinite long thread carries a charge uniformly spread over its length. It is bent in the form as shown. If the charge per unit length is $\lambda$. the electric field at point O is
                   
           (1) $\frac{\mathrm{\lambda }}{2{\mathrm{\pi \epsilon }}_0\mathrm{r}}$                                          (2) $\frac{\mathrm{\lambda }}{\sqrt{2{\mathrm{\pi \epsilon }}_0}\mathrm{R}}$

           (3) $\frac{\mathrm{\lambda }}{2\sqrt{2{\mathrm{\pi \epsilon }}_0\mathrm{R}}}$                                   (4) Zero