Explain the arrangement of orbitals in increasing order of energy on the basis of the $(n + l)$ rule.

(N/A) The energy of an orbital is determined by the $(n + l)$ rule,where $n$ is the principal quantum number and $l$ is the azimuthal quantum number.
Rules for determining energy:
$1$. The orbital with the lower value of $(n + l)$ has lower energy.
$2$. If the $(n + l)$ values are the same,the orbital with the lower value of $n$ has lower energy.
Based on these rules,the increasing order of energy is: $1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p$.

Orbital and Values	Comparison
$1s: n=1, l=0, n+l=1$	-
$2s: n=2, l=0, n+l=2$	-
$2p: n=2, l=1, n+l=3$ $3s: n=3, l=0, n+l=3$	$2p$ $(n=2)$ has lower energy than $3s$ $(n=3)$
$3p: n=3, l=1, n+l=4$ $4s: n=4, l=0, n+l=4$	$3p$ $(n=3)$ has lower energy than $4s$ $(n=4)$
$3d: n=3, l=2, n+l=5$ $4p: n=4, l=1, n+l=5$	$3d$ $(n=3)$ has lower energy than $4p$ $(n=4)$