Marvin was not aware he had to write due diligence notes for taxpayers claiming the head of household filing status. The IRS conducted a due diligence audit of $20$ tax returns Marvin prepared in $2024.$ Of those, seven filed using the head of household filing status. These seven returns were the only ones Marvin was penalized for and it was only related to his failure to include due diligence notes related to the head of household filing status. What will Marvin's penalty be$?$

$$4,200$

$$12,000$

$$16,800$

$$48,000$