During 2001, a stock lost 80 percent of its value

During 2001, a stock lost 80 percent of its value. During the following year, the stock's value increased by 100 percent. Which of the following is the percent change in the stock's value during those two years?

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 #12843