The Radioactivity Due to Carbon-14 Measured in a Piece of a Wooden

The radioactivity due to carbon-14 measured in a piece of a wooden casket from an ancient burial site is found to produce 20 counts per minute from a given sample,whereas the same amount of carbon from a piece of living wood produces 160 counts per minute.The half-life of carbon-14,a beta-minus emitter,is 5730 years.What would we calculate for the age of the artifact,assuming that the activity for living wood has remained constant over time?

A) 5,700 years
B) 11,500 years
C) 14,800 years
D) 17,200 years
E) 23,000 years