x_{8} = x_{3} + x_{5} + x_{2} + x_{6} + x_{1} + x_{4}\\
1 \cdot k_{18} \cdot x_{1} + 1 \cdot k_{18} \cdot x_{2} + 1 \cdot k_{18} \cdot x_{3} + 1 \cdot k_{18} \cdot x_{4} + 1 \cdot k_{18} \cdot x_{5} + 1 \cdot k_{18} \cdot x_{6} + 1 \cdot k_{18} \cdot x_{7} = k_{18} \cdot k_{19}