(a) Both arguments are correct.
(b) Cr and Cu have anomalous electronic configurations. This is because half filled and completely filled sub-shells have extra stability due to the symmetrical distribution of electrons maximum exchange energy.
24Cr = 1 s2 2s2 2p6 3s2 3p6 3d5 4s1
OR
[Ar]3d5 4s1 This is due to the extra stability of half filled 3d5 sub-shell.
29Cu = 1 s2 2s2 2p6 3s2 3p6 3d5 4s1
OR
[Ar]3d10 4s1This is due to the extra stability of completely filled 3d10 sub-shell.