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\sum_{\mathrm{k}=1}^{\mathrm{n}} \mathrm{f}\left(\mathrm{c}_{\mathrm{k}}\right) \Delta \mathrm{x}_{\mathrm{k}} \leq \sum_{\mathrm{k}=1}^{\mathrm{n}} \mathrm{g}\left(\mathrm{c}_{\mathrm{k}}\right) \Delta \mathrm{x}_{\mathrm{k}} \text { so } \lim _{\text {mesh } \rightarrow 0}\left(\sum_{k=1}^{n} f\left(c_{k}\right) \Delta x_{k}\right) \leq \lim _{\operatorname{mesh} \rightarrow 0}\left(\sum_{k=1}^{n} g\left(c_{k}\right) \Delta x_{k}\right)