Hi, I am not understanding the formula on how to figure out how much he needs to increase his withholding on this question.

This year Lloyd, a single taxpayer, estimates that his tax liability will be $10,600 Last year, his total tax liability was $15,400. He estimates that his tax withholding from his employer will be $8180.

A. How much does Lloyd need to increase his withholding by (for the year), in order to avoid the underpayment penalty?

B. Assuming Lloyd does not make any additional payments, what is the amount of his underpayment penalty? Assume the federal short-term rate is 5 percent. (Negative amounts should be indicated by a minus sign. Round your answers to 2 decimal places.)

Dates Actual Withholdings Required Withholdings Over (Under) Withheld Penalty Per Quarter April 15th June 15th September 15th January 15th Total