Added a challenge question in 01-run-quit.md for changing an existing code cell to markdown
Added a challenge question in 01-run-quit.md for changing an existing code cell to markdown

easyreporting/fmri_reporting,easyreporting/fmri_reporting,easyreporting/fmri_reporting,easyreporting/fmri_reporting,easyreporting/fmri_reporting,easyreporting/fmri_reporting