The given function is:
Where f(x) is the amount of a radioactive element remaining (in becqurels) in the area x years after 1986.
We need to find f(120) in order to determine the amount of becqurels in 2106. So:
The amount of becqurels in 2106 would be 1059.3
This value is greater than 800, and the problem says only areas with less than 800 Bqs are considered safe for human habitation. Thus, this area is not safe, because, by 2106, the radioactive element remaining in the area is greater than 800 Bqs.