It is April $5$th and the client comes into the office. His tax liability for the prior tax year was $$20,000$ based on the prior tax return. His AGI last year was $$100$K and he thinks he earned $10\%$ more the most recent tax year based on your interview. His employer withheld $$15,000$ for federal taxes throughout the tax year. If he wants to extend his tax return, what should his estimated tax payment be with his extension?