Krete is an unmarried taxpayer with income exclusively from wages. By December 31, year 1, Krete's employer has withheld $16,000 in federal income taxes and Krete has made no estimated tax payments. On April 15, year 2, Krete timely filed for an extension request to file her individual tax return, and paid $300 of additional taxes. Krete's year 1 tax liability was $16,500 when she timely filed her return on April 30, year 2, and paid the remaining tax liability balance. What amount would be subject to the penalty for underpayment of estimated taxes?