QR Decomposition

The Problem

Let

$A=\left(\begin{array}{cc}1& 1\\ 0& 1\\ 1& 0\end{array}\right).$

1. Find a QR decomposition of $A$ using the Gram-Schmidt process. That is, write $A=QR$ where $Q$ has orthonormal columns and $R$ is upper triangular with positive diagonal.
2. Why is QR decomposition useful for solving least-squares problems ${\min }_x\Vert Ax-b{\Vert }^2$?