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By definition of subshell labels: $5d\rightarrow n=5, \ell=2$ and since $-\ell\leq m_\ell\leq \ell$, valid $(n,\ell,m_\ell)$ sets are: (5,2,-2), (5,2,-1), (5,2,0), (5,2,1) and (5,2,2).
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