Zach is single with no dependents. He is not claimed as a dependent on another's return. All

Question:

Zach is single with no dependents. He is not claimed as a dependent on another's return. All of his income is from salary and he does not have any for AGI deductions. What is his earned income credit in the following alternative scenarios?
a. Zach is 29 years old and his AGI is $5,000.
b. Zach is 29 years old and his AGI is $10,000.
c. Zach is 29 years old and his AGI is $19,000.
d. Zach is 24 years old and his AGI is $5,000.