Find the least square solution of Ax=b where

$$ A=\begin{bmatrix}
1 & -3 & -3\\
1 & 5 & 1\\
1 & 7 & 2\\
\end{bmatrix}, b= \begin{bmatrix}
5\\
-3\\
-5\\
\end{bmatrix}$$

and compute the associated least square error.