What, if anything, does each one of the following tell you about ease of entry into or exit from an industry?
a. Profits have been very high for two decades.
b. No new firms have entered the industry for 20 years.
c. The average age of the firms in the 40-year-old industry is less than 7 years.
d. Most existing firms are using old-technology equipment alongside newer, more modern equipment.
e. Profits are low or negative; many firms are still producing, but from steadily aging equipment.