Squashed 'Session 3/' content from commit c1f6166

git-subtree-dir: Session 3
git-subtree-split: c1f6166762bcc90ad62d75f8da2c5dd33ea29075
Merge commit '74739770aa2785254b1e4b60c589d83ce63e69e3' as 'Session 3'
Updated subtree notes.