The rational brain is associated mostly with the:

The rational brain (neocortex) is associated mostly with the thinking and language. It assists us with functions related to thinking and language like planning, making decisions, solving problems, and generating new ideas. It is a functional layer of the brain, connected to the emotional brain. It also influences in a myriad of ways and providing rich data.

The rational brain stays out of the limbic system. The neocortex (very thin outermost layer of the cortex) is responsible for higher-order thinking and symbolic communication and long-term planning.

the factors that the economies of the muslim empires prosper were:

1- land trade routes-located between three continents  

2- sea trade routes

trade contributed to the spread of muslim empires, and with that islamic culture led to a growing feeling of internationalism resulted in the transfer of technology, science, and other cultural forms.

a would be the answer