If the system of equations 2 x+y-z=5; 2 x-5 y+λ z=μ; x+2 y-5 z=7 has infinitely many solutions, then (λ+μ)^2+(λ-μ)^2 is equal to

If the system of equations $$\begin{aligned} & 2 x+y-z=5 \\ & 2 x-5 y+\lambda z=\mu \\ & x+2 y-5 z=7 \end{aligned} $$ has infinitely many solutions, then $\displaystyle (\lambda+\mu)^2+(\lambda-\mu)^2$ is equal to