Which of the following individuals are required to file a tax return for 2019? Should any of these individuals file a return even if filing is not required? Why or why not? 

a. Patricia, age 19, is a self-employed single individual with gross income of $5,200 from an unincorporated business. Business expenses amounted to $4,900. 

b. Mike is single and is 67 years old. His gross income from wages was $10,800. 

c. Ronald is a dependent child under age 19 who received $6,800 in wages from a part-time job. 

d. Sam is married and files a joint return with his spouse, Lana. Both Sam and Lana are 67 years old. Their combined gross income was $24,250. 

e. Quinn, age 20, is a full-time college student who is claimed as a dependent by his parents. For 2019, Quinn has taxable interest and dividends of $2,500.