Let $A = \sum_{k=0}^{p} a_k X^k$ be an element of $\mathbb{K}[X]$, of degree $p \geqslant 0$, which without loss of generality we assume to be monic.
Determine $\mathcal{R}_A(\mathbb{K})$ when $A = X^p$ (with $p \geqslant 1$) and give a basis for it.