Samoa was a stopping point for the US Merchants.
I believe the answer is: 2. but should be abolished.
The abolitionists see slavery as inhumane and should be stopped. This view become even more popular after the industrial revolution that come from western Europe, which eliminate the needs of using slave labour since it can be replaced with machines.
Well they used the tribute as sort of a tax for the empire. it helped them advance in troops architecture and religion