Answer:
It is the 2nd option
Step-by-step explanation:
168
132, 135, 138, 141, 144, 147, 150, 153, 156, 159, 162, 165, 168
240 days is 4 times the half-life, which means that a sample of 1000 mg will decay to
after 240 days.
20
There are 10 feet of posts on each side. That means there are 40 feet of fencing in total. If you divide that by two (to represent posts being 2 feet apart) then you get 20. There are 20 posts needed.