Chapter 4.1, Problem 4E

Let $m\ge n$, let A be the $m\times n$

identity matrix (the principal submatrix of the $m\times m$ identity matrix), and let $b=\left[b_1,\mathrm{...},b_m\right]$

be a vector. Find the least squares solution of $Ax=b$

and the 2-norm error.