Choice B is the correct answer. Find $r$ from $b = 1 - r$.

1. Identify Factor: $b = 0.8$.
2. Solve for r: $0.8 = 1 - r \implies r = 0.2$.
3. Convert: $0.2 = 20\%$.

💡 Strategic Tip: If you keep 80%, you lost 20%.

Choice A is incorrect because 80% is what remains. Choice C is incorrect because it confuses decimal places.