This year, Santhosh, a single taxpayer, estimates that his tax liability will be $100,000. Last year, his total tax liability was $15,000. He estimates that his tax withholding from his employer will be $35,000. a. Is Santhosh required to increase his withholding or make estimated tax payments this year to avoid the underpayment penalty? Yes No b. By how much, if any, must Santhosh increase his withholding and/or estimated tax payments for the year to avoid underpayment penalties?