How did the north profit of slave labor

The north also profited from slavery through taxes. The taxes in the north were lower because of the tariffs collected on imports of goods financed by cotton exports. A large surplus was extracted from slaves and the bulk of the surplus went to those in the north whose taxes were lower than would otherwise have been if not for the slaves.

Explanation:

The north profited from slavery through taxes. The taxes in the north were lower because of the tariffs collected on imports of goods financed by cotton exports