Answer:
F=50
Step-by-step explanation:
F=5*10=50
I believe it would be 12.16
A. 2.8 billion years old
1/16 = (1/2)^4, so 4 half-lives have elapsed.
4 · 0.700 billion years = 2.8 billion years
The rock is 2.8 billion years old.