Half Life of a radioactive sample?

An ancient club is found that contains 190 g of pure carbon and has an activity of 5 decays per second. Determine its age uming that in living trees the ratio of 14C/12C atoms is about 1.2x10^-12. Note that the half life of carbon-14 is 5700 years and the Avogadro number is 6.02x10^23.