\begin{equation}
   R_{\mathcal{L}_r}(f^*) - R_{\mathcal{L}_r}(f^*_\eta)\ge  (R^\eta_{\mathcal{L}_r}(f^*) - R^\eta_{\mathcal{L}_r}(f^*_\eta))/(1-\frac{N\eta}{N-1}) + C \ge  C, 
\label{eq_b2}
\end{equation}
