1 \cdot k_{21} \cdot x_{1} + 1 \cdot k_{21} \cdot x_{2} + 1 \cdot k_{21} \cdot x_{3} + 1 \cdot k_{21} \cdot x_{4} = k_{21} \cdot k_{22}\\
1 \cdot k_{21} \cdot x_{5} + 1 \cdot k_{21} \cdot x_{6} = k_{21} \cdot k_{23}\\
1 \cdot k_{21} \cdot x_{5} + 1 \cdot k_{21} \cdot x_{9} + 1 \cdot k_{21} \cdot x_{10} = k_{21} \cdot k_{24}\\
1 \cdot k_{21} \cdot x_{7} + 1 \cdot k_{21} \cdot x_{8} = k_{21} \cdot k_{25}