Krete is an unmarried taxpayer with income exclusively from wages. by december 31, year 1, krete’s employer had withheld $16,000 in federal income taxes, and krete had made no estimated tax payments. on april 15, year 2, krete timely filed an extension request to file her individual tax return and paid $300 of additional taxes. krete’s year 1 income tax liability was $16,500 when she timely filed her return on april 30, year 2, and paid the remaining income tax liability balance. what amount is subject to the penalty for the underpayment of estimated taxes?