A micropaleontologist uses stable isotope analysis to date a sediment core. She finds that the ratio of oxygen-18 to oxygen-16 decreases by 0.3% every 1,000 years. If the current ratio is 2,000 parts per million (ppm), and the baseline ratio 10,000 years ago was higher, how many ppm was the ratio 10,000 years ago, assuming exponential decay? - Portal da Acústica