1 \cdot k_{19} \cdot x_{2} + 1 \cdot k_{19} \cdot x_{4} + 3 \cdot k_{19} \cdot x_{6} + 3 \cdot k_{19} \cdot x_{8} = k_{19} \cdot k_{20}\\
1 \cdot k_{19} \cdot x_{7} + 1 \cdot k_{19} \cdot x_{8} = k_{19} \cdot k_{21}