A shopkeeper purchased 77 kg of potatoes for Rs

A shopkeeper purchased 77 kg of potatoes for Rs. 539 and sold the whole lot at the rate of Rs. 8.50 per kg. What will be his gain percent?

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #47935