[填空题]
The practical limit for carbon-14 dating is about 60,000 yeahi2hb / 8pw-nt qf0c419xb ocqrsd)a *2 dgxs.0lzxvn2w . If a bone contains 1.0 kg of carbon, and the animal died 60g0.nvdd w2xz)a2 *xsl,000 years ago, what is the activity today? $\ \text{decays/s}$
