1)
Why does it say "v'Al ha'Sabalim u'Menatzchim"?
1.
Malbim: [The Leviyim who knew song were appointed] also over the carriers. Additionally there were supervisors ? one for each kind of task.
2)
What do the Sofrim of the Leviyim do?
1.
'Rashi': They count the money brought to Beis Hashem.
3)
What do the Shotrim do?


