 \\ &= \sum_{\mathbf{b} \in \mathcal{Z}_n, \mathbf{b}\neq0} \mathcal{C}_0 \frac{\mathcal{C}_0(0-e^{- \lambda_{0} \gamma_{t,d}})-\lambda_0(0-e ^{- \mathcal{C}_0 \gamma_{t,d}}) }{\lambda_0-\mathcal{C}_0}. \end{split}$$  