The ratio of 14C12C1351012 stays constant in living organism

The ratio of 14C/12C=1.35*10^-12 stays constant in living organisms and the half-life of 14C is 5730 years.

If your measurement of 14C/12C has an uncertainty of 1%, what are the upper and lower limits on dating in years that you can reliably measure?

Can someone please show how to solve this.

For a first order reaction

Kt = ln[Ao]/[A]
or, 0.693/5730 *t = ln[Ao]/0.7[Ao] =ln10/7 = 0.3567
or, t=5730*.3567/.693 =2949.13 years (Ans)