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\begin{aligned}&=c_{r_{1}} i_{e}\left[n \int_{0}^{M}(M-t) D_{c} d t+\int_{0}^{T^{\prime}}\left(T^{\prime}-t\right) D_{c} d t+\left(M-T^{\prime}\right)\left(p_{m} T_{s}-n D_{R}\right)\right] \\&=\frac{n c_{r_{1}} i_{e} D_{c} M^{2}}{2}+\frac{c_{r_{1}} i_{e}}{2}\left(p_{m} T_{s}-n D_{R}\right)\left(2 M-T^{\prime}\right)\end{aligned}