For 2013,Randy,an Unmarried Taxpayer,has Wages of $45,000

For 2013,Randy,an unmarried taxpayer,has wages of $45,000.He has a significant amount of income from dividends and interest and therefore expects to have a federal income tax liability of $18,000.His total federal income tax withholding for the year is $9,500.Randy had $100,000 of adjusted gross income and a federal tax liability of $11,000 on his 2012 return.To avoid a penalty for underpayment of estimated taxes,what is the minimum amount of total estimated tax that Randy must pay in 2013? Assume the payments are made on a timely basis.