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\lim _{\text {mesh } \rightarrow 0} \mathrm{YS}_{\mathrm{P}}=3 \text { and } \lim _{m e s h \rightarrow 0} \mathrm{FS}_{\mathrm{P}}=6 \text { so } \lim _{m e s h \rightarrow 0}\left(\sum_{k=1}^{n} f\left(c_{k}\right) \cdot \Delta x_{k}\right)