How does one sings gregorian chants? enumerate the process

Supply and Demand is directly linked to Price x Demand.

In Economics, the connection between goods (or services) that are being offered for a certain price and their demand is called Supply Relationship. The Law of Supply states that there is a direct relationship between the prices of products and services and the supply. So, if there is an increase in the price of these goods and services, the supply for those will increase, as well.  

the awenser wuold be slaves

c, because the american revolution was from 1765 to 1783.