Consider the meter bridge circuit without neglecting end corrections. If we used $100\Omega$ and $200\Omega$ resistance in place of R and S respectively, we get null deflection at ${\mathcal{l}}_1=33.0$ cm. If we interchange the resistances, the null deflection was found to be at ${\mathcal{l}}_2=67.0$ cm. If $\alpha$ and $\beta$ are the end correction, then the value of $\alpha +\beta$ should be