24. In 2020, Katrina filed her 2019 Form 1040. She mailed her extension on March 15 certified mail. The return receipt shows the IRS received it April 14. She mailed her return on October 1 certified mail. The return receipt shows the IRS received it October 21. Assume she filed a valid and true return. When was Katrinas return filed? Select one: a. April 14 b. April 15 c. October 1 d. October 15 e. October 21.