Hello pls help!!

The half-life of carbon-14 is 5,730 years. Suppose a fossil is found with 20 percent as much of its carbon-14 as compared to a living sample. How old is the fossil?
A. 13,307 years
B. 3,235 years
C. 1,331 years
D. 32, 346 years

Please help it's very urgent!!