x_{1} = k_{7} + \operatorname{piecewise}(k_{8}, t \le k_{11}, 0) + k_{9} \cdot t / k_{12}\\
1 \cdot k_{13} \cdot x_{4} + 1 \cdot k_{13} \cdot x_{5} + 1 \cdot k_{13} \cdot x_{6} + 1 \cdot k_{13} \cdot x_{8} = k_{13} \cdot k_{27}\\
1 \cdot k_{13} \cdot x_{7} + 1 \cdot k_{13} \cdot x_{8} + 1 \cdot k_{13} \cdot x_{9} = k_{13} \cdot k_{28}