Let $k$ be a field and consider the exterior algebra $$\Lambda^{\bullet} k = k \oplus k\{1\}$$ where $k$ is seen as a vector space over itself. Consider the abelian category $\mathcal{A}$ of graded modules over $\Lambda^{\bullet}k$. I would like to compute $${\rm{Ext}}_{\mathcal{A}}^{i}(k,k \{j\})$$ where $\{ j\}$ denotes the shift of the grading of a module.
Thank you very much for your help.