So, basically the question is asking what is the dose of a medication that is 2.5mg/kg.
Assuming that the child does NOT weigh 7171lbs but 71lbs; which would equal around 32kg (71 x 0.45).
So this child would have 2.5mg per 32kg. 32kg x 2.5= 80mg of medication.
The one that could be contracted from airborne germs is : Chicken pox
Which why it spread easily. By being in the same room with an infected, you're very likely to be exposed with the viruses even though you never made a contact with the infected
hope this helps