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\begin{aligned} &c_{h} \int_{t_{i-1}}^{t_{i}^{p}} e^{-\alpha t}\left[\int_{t_{i-1}}^{t} e^{\alpha u}\{p-D(u)\} d u\right] d t \\ &\quad+c_{h} \int_{t_{i}^{p}}^{t_{i}} e^{-\alpha t}\left\{\int_{t}^{t_{i}} e^{\alpha u} D(u) d u\right\} d t+c_{1} \int_{t_{i-1}}^{t_{i}^{p}} p d u \end{aligned}