This is a bit subjective, but it could be argued that social change had the biggest change in Southern life, since the abolition os slavery (which was inherently a social issue) led to the biggest changes.
The answer is: The middle colonies experienced economic growth as cities such as New York and Philadelphia became centers of trade.
When both new york and Philadelphia become the centers of trade, a lot of investors became interested to inject their capital into these two cities.
This created a lot of job opportunities in both of these cities, making the middle colonies around them to experience massive economic growth and increase in the number of modern infrastructures.
Answer:
A Pool
Explanation:
Given that a POOL is a form of business strategy where competing business firms come together to form an agreement or union that is based on maximizing profits by reducing competition through controlling prices.
Hence, in this case, where two competing railroad companies agreed to fix shipping rates at a level that benefited both. This kind of voluntary arrangement is called "A POOL."