Vertical alignment with cases environment

Question

I hope this question is not duplicate: How is it possible to align all of these equals signs? The main problem is the cases environment, because I don't know how to reference the &-Operator.

Thank you very much in advance!

\documentclass{scrartcl}
\usepackage{amsmath}
\usepackage{mathtools}
\begin{document}

\begin{align*}
a+b&=0
\intertext{some text a}
c+d&=0
\intertext{some text b}
\begin{rcases}
\lambda_a &= x\\
\lambda_b &= y
\end{rcases} \quad \text{some text c}
\end{align*}

\end{document}

Answer 1

Another possibilities is use split environment instead rcases and added curly brace after it:

\documentclass{scrartcl}
    \usepackage{mathtools}

\begin{document}
    \begin{align*}
a+b &=0
\intertext{some text a}
c+d &=0
\intertext{some text b}
\begin{split}
\lambda_a &= x\\
\lambda_b &= y
\end{split}\;\bigg\} \quad \text{some text c}
    \end{align*}
\end{document}

Result:

Answer 2

This is one way to obtain the same formula structure and have the equal signs line up.

\documentclass{scrartcl}
\usepackage{amsmath}
\begin{document}

\begin{align*}
& a+b =0 \text{ some text a } \\
& c+d =0 \text{ some text b } \\
& \hspace{1.5mm} \left. \begin{array}{l} \lambda_{a} = x \\
  \lambda_{b} = y \end{array} \right\} \quad \text{ some text c } 
\end{align*}

\end{document}