The half-life carbon-14 is 5730 years. archaeologists dig up a seed that contains 0.25 parts per trillion of carbon-14. if it originally contained 1 part per trillion carbon-14, how old is the archaeological specimen?

a) 11,460 years

b) 5730 years

c) 17,190 years

d) 22,920 years

e) 28,650 years

how do you get 11,460 which is the answer of to this problem?