Final answer:
Bob, age 45, has already contributed the maximum amount to his 401(k) this year, so he may not contribute any amount to his Roth 401(k). The correct answer is c.) $0.
Step-by-step explanation:
Bob, age 45, contributes $19,500 to his 401(k) this year.
The limit for 401(k) contributions for individuals under 50 years old in 2021 is $19,500. Therefore, Bob has already contributed the maximum amount to his 401(k) this year.
Since Bob has contributed the maximum amount to his 401(k), he may not contribute any amount to his Roth 401(k) this year. The correct answer is c.) $0.