Answer:
Peter's failure to file penalty = $700
Step-by-step explanation:
Peter filed tax return on July 31 after forgetting to file his tax return by April 15 and did not ask for extension. This means that the IRS can impose a 20% penalty on Peter for the tax due on a return where there is negligence, as can be established in this case.
Peter's remaining tax liability = $3,500
Penalty = $700 ($3,500 * 20%)