please show all calculations.

6. Chan, a single 35-year-old CPA, is covered by a qualified retirement plan at work. His salary is $120,000, and his total AGI is $129,000. The maximum contribution he can make to a Roth IRA in 2020 is A) 0. B) $2.400 C) $4,000 D) $6,000 6. Chan, a single 35-year-old CPA, is covered by a qualified retirement plan at work. His salary is $120,000, and his total AGI is $129,000. The maximum contribution he can make to a Roth IRA in 2020 is A) 0. B) $2.400 C) $4,000 D) $6,000