The answer is A.
This is saying 5E-9/2E4, so it equals 2.5E-13.
Viruses spread more easily now than a long time ago due to the fact that people didnt care about the current virus. They stopped wearing masks, which started to bring more, colds, sickness, and viruses, and now, people are spreading viruses faster than before.
Step 1- multiply 40 by 25 to get 1000
step2- multiply 8 by 5 to get 40
step3- divide 1000 by 4 to get 250
answer. 250 pieces