Answer:
5727 years or 5730 (rounded to match 3 sig figs) whichever one your teacher prefers
Explanation:
First Order decay has a half life formula of Half Life = Ln (2) / k = 0.693/K
Half-life = 0.693/k = 0.693/1.21 x10-4 = 5727 years or 5730 (rounded to match 3 sig figs)
This should be correct because if you google the half-life of 14 C it is ~ 5700 years