Typo in second paragraph first sentence of Section 6.6

[Jarell-Cheong]

The first sentence of the second paragraph of Section 6.6 starts with:

Let $\mathcal{C}(\mathbb{X})={ \mathbb{X}\mathbf{b}\colon \mathbb{b}\in \mathbb{R}^2} be the column space...

This should be:

Let $\mathcal{C}(\mathbb{X})={ \mathbb{X}\mathbf{b}\colon \mathbb{b}\in \mathbb{R}^{k+1}} be the column space...

(replaced $2$ with $k+1$ in the dimension of the Euclidean space since outside of examples, it is assumed that $\mathbb{X}$ is a $n\times(k+1)$ matrix)