The answer in the space provided in the sentence above is
wampum, this is the material that the woodlands people used in keeping records
or exchange conclusion of treaties. Wampum is small cylindrical beads used for
either as a decorative display, accessory or they could also use this as their
own money.
as an empire on top of mountains so no intruders could get in.
This is an example of exchange theory.
In sociology, exchange theory has to do with maximizing benefits while also minimizing costs. When applied to Bill and Cathy's situation, they are taking advantage of each other's skills in order to minimize costs - Bill can cook and Cathy can't (so they can prepare food on their own) and Cathy can repair stuff and Bill can't (so they don't have to get a handyman).
The price will fall, because a fall in demand causes a fall in the price.
