The amount of product available.

The amount of a product people are willing to buy or produce.  

A point that the price isn't allowed to fall below.  

A cost that doesn't vary no matter how many goods are produced.

Costs that vary depending on how much a product is produced or sold.  

One person owns and operates a business.

Two or more people operate a business.

A company or group acting as a single person according to the law.