As an investor, you’ll want to invest only in businesses that are likely to be profitable in the long run. Assess the barriers to entry in each of these markets, with an eye to forecasting whether they’ll yield positive economic profits in the long run. 

a. The market for lawn-care services. 

b. The market for wireless telecommunications, such as mobile phone service. 

c. The market for sport-utility vehicles. 

d. The market for generic aspirin.