Gabriel O'Scatterbrain receives a notice from his local IRS office indicating that his 2013 return is being audited, in particular his Schedule C which shows gross receipts of $222,000. The letter informs Gabriel that an appointment has been scheduled on June 30, 2014, at 10:00 a.m. for him to come to the office. He is told to bring with him copies of the documentation which will substantiate his claimed travel expenses and his deduction for meals and entertainment. The letter also requests that he provide documentation supporting his gross receipts of $222,000. This is an example of what method of conducting an audit? What alternative methods are available? Explain each.