3520:20 should be correct
Answer:
We have 197 g of Co-60 after 18 months.
Step-by-step explanation:
We can use the decay equation.

Where:
- M(f) and M(i) are the final and initial mass respectively
- λ is the decay constant (ln(2)/t(1/2))
- t(1/2) is the half-life of Co
- t is the time at the final amount of m
<u>Therefore, we have 197 g of Co-60 after 18 months.</u>
I hope it helps you!
What exactly are you asking. Are you asking for area or perimeter?