Answer:
48
Step-by-step explanation:
n/-3=-16
n=-16*-3
n=48

The answer is above.
Additional note 1:

Additional note 2:
In the answer I filled in "0" at the place where "n" was. This is because the question tells us n=0
1.75 Grams is what I got. Every 1 Milligram = 0.001 Gram.
Hope it helps :)
I believe it is D, stratified random sampling.
Hope this helps!!