You should have a 3 digit number after rounding and multiplying by 1000. Substitute that number in the following url at the end in place of nnn:

https://robert-nicoud.ch/vivian/ap-calculus-ab/caching-games/caching-game-2/caching2-nnn/

Copy-paste the url in your browser and if you solved the question correctly, you’ll find the next question. On the other hand, if you reach a “404: Page not found”, that means you made a mistake…