Julie, a self-employed individual, is required to make estimated payments of her tax liability for the year. Her tax liability for 2020 was $25,000, and her AGI was less than $150,000. For 2021, Julie ultimately determines that her income tax liability is $18,000. During the year, however, she made the following payments, totaling $13,000: April 15, 2021 $4,500 June 15, 2021 2,800 September 15, 2021 4,100 January 18, 2022 1,600 Total paid $13,000 Because Julie prepaid so little of her ultimate income tax liability, she now realizes that she may be subject to the penalty for underpayment of estimated tax. If an amount is zero, enter "O". b. If Julie's tax liability for 2020 was $15,960, determine Julie's penalty for underpayment of estimated tax, if any. Julie's required annual payment for estimated taxes should have been $ 15,960, and each quarterly installment would have been $ 3,990 The underpayments are as follows. First installment (April 15, 2021): $ o 680 Second installment (June 15, 2021): $ Third installment (September 5, 2021): $ Fourth installment (January 15, 2022): $