Answer:
The answer is t = 11361 years
Explanation:
The amount left has the relationship with the original amount (nuclear reaction)
N  = N0 e^−t/τ  (τ is the time constant for the e^−1 life.
half-life = Â 5730 years for 14C
0.5 N  = N0 e^−t/τ ---> τ  = t1/2 / ln2 = 8266.64 years
Thus, for 25.3% of original amount of 14C, the time needed is:
t = Ï„ ln (N0/N)
t = 8266.64 * ln (N0/0.253N0)
t = 11361 years