1 \cdot x_{1} + 1 \cdot x_{2} = k_{20}\\
1 \cdot x_{3} + 1 \cdot x_{4} = k_{21}\\
1 \cdot x_{5} + 1 \cdot x_{6} = k_{22}\\
1 \cdot x_{7} + 1 \cdot x_{8} = k_{23}