User blog comment:Visually/Don't do "Summer's Over Update" before claim your mastery rewards./@comment-109.80.17.101-20151014125318/@comment-26536836-20151017023159

I don't think Biome's challenge 15 give good credit. So pro-ing isn't good for farming--and probably it has long track.

I think just max to do Season 9 race would be better.

I think A or S class' challenge 15 gives quite good credit so if there has short track(can finish less than a minute), it might be good farming spot.