Scientists can determine the age of ancient objects by a method called radiocarbon dating. The bombardment of the upper atmosphere by cosmic rays converts nitrogen to 14C ,a radioactive isotope of carbon, with a half-life of about 5730 years. Vegetation absorbs carbon dioxide through the atmosphere and animal life assimilates 14C through food chains. When a plant or animal dies, it stops replacing its carbon and the amount of 14C begins to decrease through radioactive decay. Therefore, the level of radioactivity must also decay exponentially. A parchment fragment was discovered that had about 13% as much 14C radioactivity as does plant material on Earth today. Estimate the age of the parchment.

Select the correct answer.

a) t= 16,724 years
b) none of these
c) t= 17,150 years
d) t= 18,373 years
e) t= 16,866 years
f) t= 16,189 years