Let $p$ be a closed point on $\mathbb{P}_{k}^{2}$, where $k$ is an algebraically closed field. Let $I_{p}$ be the ideal sheaf at $p$, then we will have an exact sequence
$$0\to I_{p}\to \mathcal{O}_{\mathbb{P}^2}\to k(p)\to 0$$
Where $k(p)$ is the corresponding skyscraper sheaf.
Now I want to calculate $\operatorname{Ext}^{2}(k(p), \mathcal{O}_{\mathbb{P}^2})$.Since $H^{1}(\mathbb{P}^2, \mathcal{O}_{\mathbb{P}^2})=H^2({\mathbb{P}^2,\mathcal{O}_{\mathbb{P}^2}})=0$, $\operatorname{Ext}^{2}(k(p), \mathcal{O}_{\mathbb{P}^2})\cong \operatorname{Ext}^{1}(I_{p},\mathcal{O}_{\mathbb{P}^2})$. But also, I do not know what should I do next. Could you help? Thanks