Construct signal flow graph for following set of system equations and hence find \(x_{4} / x_{1}\).

\[
\begin{aligned}
& x_{2}=k_{1} x_{1}+k_{3} x_{3} \\
& x_{3}=k_{4} x_{1}+k_{2} x_{2}+k_{5} x_{3} \\
& x_{4}=k_{6} x_{2}+k_{7} x_{3}
\end{aligned}
\]