Carbon-14, a naturally occurring unstable isotope of carbon, has a half-life of 5730 years. Answer the questions below.
In a sample of carbon containing 2.5 parts per trillion of carbon-14 (that is, 2.5 carbon-14 atoms per every 10^12 atoms of carbon), how much carbon-14 remains after 22920 years?
After 22920 years, _______ parts per trillion of carbon-14 remains in the sample.
Carbon-14 is used for a technique called "carbon dating", which uses the radioactive decay of carbon-14. If it can be determined that an artifact originally had 9.50×10^9 carbon-14 atoms originally but now only has 2.969×10^8 carbon-14 atoms (carbon-14 having decayed into other isotopes, such as nitrogen-14), how old do you estimate the artifact to be?
The artifact is estimated to be ________ years old.