[填空题]
(a) A 92-gram sample ofx75g e (ltf5j,bl xz8-4g(et(rq cx sjf+qsm dhfdyc +: n1x t(0lt:x(natural carbon contains the usual fraction of $_{6}^{14}\text{C}$. Estimate how long it will take before there is only one $_{6}^{14}\text{C}$ nucleus left. t = $ \times 10^{5}\ \text{yr}$2.4
(b) How does the answer in (a) change if the sample is 280 grams? What does this tell you about the limits of carbon dating? $10^a$yr a =
