Each of the following firms benefits from barriers to entry in its industry. Indicate whether each of the barriers is natural or government created.

a. A small-town bar that is the only establishment in the county licensed to serve liquor.
b. A diamond company that owns nearly all of the world's diamond mines
c. A pharmaceutical company receives a patent for a new cancer-fighting drug
d. A soda company that spends over $3 billion on advertising every year
e. A waste-treatment plant that cost a lot to build even though it costs only two cents to treat each gallon of waste