A pharmaceutical company received …15 million in sales of generic equivalent of…

A pharmaceutical company received $2 million in royalties on the first $15 million in sales of generic equivalent of one of its products and then $6 million in royalties on the next $72 million in sales. By approximately what percent did the ratio of royalties to sales decrease from the first $15 million in sales to the next $72 million in sales?

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 #6851