For each of the following situations (none of the taxpayers claim dependents), indicate whether the taxpayer(s) is (are) required to file a tax return for 2016. Explain your answer.
a. Helen is a single taxpayer with interest income in 2016 of $8,750.
b. Joan is a single college student who is claimed as a dependent by her parents. She earned $1,550 from a part-time job and has $1,150 in interest income.
c. Leslie (age 64) and Mark (age 66) are married and file a joint return. They received $17,800 in interest income from a savings account.
d. Ray (age 60) and Jean (age 57) are married and file a joint tax return. They had $14,700 in interest income.
e. Harry, a 19-year-old single taxpayer, had net earnings from self-employment of $1,500.