Carbon-14 has a half-life of 5730 yrs. A living organism has an activity of 15.2 counts per minute (cpm) per gram of carbon. If a bone is determined to have an activity of 3.80 cpm per gram of carbon, how old is the bone?
A. 5,730 yrs
B. 17,200 yrs
C. 22,900 yrs
D. 8,600 yrs
E. 11,500 yrs