Solution
= Solution
Substituting $\beta=1$ and $\gamma=1-\alpha$ into the <matrix> gives
$$
\boxed{A_\alpha=\begin{pmatrix}\alpha+1&1-\alpha&2\\2&\alpha&2-\alpha\\2-\alpha&\alpha+3&1\end{pmatrix}.}
$$
Its row sums are $4,4,6$, checking that $A_\alpha\mathbf c=\mathbf b$ for every real $\alpha$.