Identify which type of market (perfect competition, perfectly contestable markets, monopolistic competition, and oligopoly and its various types) these conditions most likely describe.

a. Few firms and high barriers to entry.

b. A Dairy Board that tells dairies how much milk to produce and requires all milk be sold to it.

c. Many restaurants in a town, each serving a slightly different menu. It is easy to enter the restaurant business.

d. One major firm dominates the computer industry but many small firms actively compete.