What is the fastest time a person can earn a Sun badge?

A few days ago I was doing my Math stuff when it came to me that it is possible for me to master skills that was extremely easy (like early math review), and I found that I should be able to master 100 skills like these in 20-30 minutes, so I basically can earn a Sun badge in half an hour. But what do you guys think is the lowest possible time for this? Thank you!