Answer
See the answer below.
Work Step by Step
By definition of subshell labels:
$4p\rightarrow n=4, \ell=1$
and since $-\ell\leq m_\ell\leq \ell$, valid $(n,\ell,m_\ell)$ sets are:
(4,1,-1), (4,1,0) and (4,1,1).
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.