Having put off for months filing his Year 1 income tax return, Bill finally decides on the evening of April 15, Year 2 ja Friday), to make an effort to file. He prepares a Form 1040 Federal Income Tax Return with an estimate of his gross income and deductions for Year 1. He signs and dates the return, includes a personal check for the estimated tax due, and rushes to the post office to mail it before midnight. He mails it by regular mail, properly addressed, with a postmark of April 15. The return arrived at the IRS on Tuesday, April 19. A On what day is Bill treated as having filed the return? B. Assume instead that Bill decides to submit a request for an extension of time to file his Year 1 return. He properly completes Form 4868. Application for Automatic Extension, and mails the form to the IRS, properly postmarked, on Friday, April 15. Year 2. The extension request estimates his Year 1 tax liability but Bill does not include any tax payment with the request. The IRS receives the extension request on April 18. When will Bill's Year 1 income tax return be due? C Assume instead that Bill mails the properly completed Form 4868 referenced in Part B, above, on April 16, Year 2. The IRS receives the extension request on April 18. On what date is Bill's Year 1 income tax return due