Physical Chemistry question from chemical kinetics

Question

A piece of wood from an archeological source shows a 14C activity which is 60% of the activity found in fresh wood today. What will be the age of the archeological sample would be (t1/2 = 5770 years)?

Answer 1

fraction remaining = 0.5n where n = # half lives that have elapsed

0.60 = 0.5ⁿ

log 0.6- =n log 0.5

0.737 = n

0.737 x 5770 yrs = 4252 years old