You are working with your self-employed individual tax client in March of 2021 to finalize his 2020 tax return and plan for 2021 estimated tax payments. In 2020, your clients AGI was $550,000 and his total tax liability was $176,000. He anticipates that his 2021 AGI will be $300,000. You calculate his 2021 tax liability will be $72,000. Please calculate the necessary estimated tax payments he is required to make.