Merge pull request #598 from abhinavc/master

Minor correction + explnatory margin note
Merge pull request #599 from abhinavc/master

new question
[cron-git-commit] @ 19.08
Merge pull request #600 from abhinavc/master

new question
[cron-git-commit] @ 22.08
Merge pull request #601 from abhinavc/master

new question
[cron-git-commit] @ 12.21
Merge pull request #602 from abhinavc/master

Sharpened logic for inserting QR code in the bottom left corner
Merge pull request #603 from abhinavc/master

Audit issues resolved
[cron-git-commit] @ 05.48
[cron-git-commit] @ 05.53
4 questions on differentiation
added a question
more questions
minor edits
- added question
question on differentiation
Merge pull request #604 from adamarla/master

Questions on differentiation
[cron-git-commit] @ 09.44
[cron-git-commit] @ 09.46