In 2021, Zach is single with no dependents. He is not claimed as a dependent on anothers 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? Use Exhibit 8-11. (Round your intermediate and final answers to the nearest whole dollar amount. Round your final answer to the nearest whole dollar amount. Leave no answer blank. Enter zero if applicable.)

a. Zach is 29 years old and his AGI is $6,300.

b. Zach is 29 years old and his AGI is $10,150.

c. Zach is 29 years old and his AGI is $18,700.

d. Zach is 17 years old and his AGI is $6,300.