Jermaine's tax liability for Year 7 was $18,000 and he had taxable income of $100,000. For Year 8 he had taxable income of $120,000 and a tax liability before withholding and estimated payments of $21,000. To avoid an underpayment of estimated tax penalty for Year 8, the minimum amount of estimated tax payments that Jermaine must make is:

$16,200.

$18,000.

$18,900.

$21,000.