Would you please answer this for the year 2020?

5. A married couple with AGI of $210,000 in 2020 has a tax liability of $38,000. The taxpayer's 2021 AGI and tax liability are $140,000 and $20,000, respectively. To avoid any penalty for underpayment of estimated tax in 2021, what is the minimum amount the taxpayer must prepay during 2021