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\begin{equation}\label{(2.3)}
\begin{array}{rl}
\min &  \displaystyle\sum_{r=1}^{s} s_r\\
 s.t & \displaystyle\sum_{\substack{ j=1\\ j\neq k }}^{n}\lambda_{j} y_{rj}\geqslant y_{rk}\qquad r=1,...,s\\
& \displaystyle\sum_ {\substack{j=1\\ j\neq k}}^n \lambda_j =1\\
& \lambda_j \geqslant 0, \quad  j\neq k  \\
& s_r \geqslant 0
\end{array} 
\end{equation}




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