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\begin{aligned} =& p\left(\frac{c_{h}}{\alpha}+c_{1}\right)\left(t_{i}^{p}-t_{i-1}\right)-\frac{c_{h}}{\alpha} e^{-\alpha t_{i}^{p}} \int_{t_{i-1}}^{t_{i}^{p}} e^{\alpha u u}\{p-D(u)\} d u \\ &+\frac{c_{h}}{\alpha} e^{-\alpha t_{i}^{p}} \int_{t_{i}^{p}}^{t_{i}} e^{\alpha u} D(u) d u-\frac{c_{h}}{\alpha} \int_{t_{i-1}}^{t_{i}} D(u) d u-c_{1} \int_{t_{i-1}}^{t_{i}} D(u) d u . \end{aligned}