Please provide examples of firms that belong to industries that are perfectly competitive, monopolistically competitive, duopolistic, oligopolistic or just pure monopolies. Explain the industry setup by providing examples of other firms (numbers) or market concentration statistics, some description of the product (is it standard, slightly differentiated, highly differentiated, or a crucial input that one firm has control of), and the nature of barriers to entry or exit in the industry (are they non-existent or significant, and what kinds of barriers these are). Please also respond to a classmate's post.