Discuss ways the economies of the upper south and the deep south became dependent on each other around 1860?

The correct answer to this open question is the following.

The ways in that the economies of the Upper South and the Deep South became dependent on each other around 1860 were the following. In the Upper South, they traded slaves. They sold and transported slaves to the Deep South region because there, slaves were needed to work in the plantations. In different regions, different crops were grown. So the sale of slaves was needed to work in the fields of the South.

the doctrine of nullification recommended that states living inside the union have the one-sided, inalienable ideal to void any law made by the national government that could be esteemed illegal.

the united states was shaped based on a general agreement among its individual states. hence, it is inferred that under the hypothesis of invalidation, since the states are the establishment of the union, they have the ability to referee and disprove unlawful laws.