Decay of Carbon

Assume that we have isolated a 1.00g sample of carbon from a frozen animal and that the half-life of C14 is 5730 yrs; ratio of C14 to C12 in the atmosphere now is $1.3×10^{-12}$ to 1.

Given the ratio of the two isotopes of carbon has not been constant throughout time and the ratio decreases by 0.1% of the current value for each century that we go back in time and the number of decays per minute now is 1, find the age of the sample to the nearest thousand.