how could i do this with using dimensional analysis?

Question

4 mL of Tylenol3 to be given every 4 – 6 hours. Your research indicates that there are 12 mg codeine per 5 mL of liquid and that the safe dosage is between 0.5 and 1 mg/kg/dose every 4 – 6 hours. Is this prescription safe and effective for your child? Explain. If not, what is the minimum and maximum dose that should be prescribed?

Answer 1

5 mL of Tylenol3 contains 12 mg codeine

Hence, by rule of proportion, 4 mL of Tylenol3 contains (12*4)/5 mg codeine = 9.6  mg codeine

every 4 – 6 hours, 1 mg of codeine can be given to child of  at least 1 kg

Hence, by rule of proportion, every 4 – 6 hours, 9.6 mg of codeine can be given to child f at least 9.6 kg.

Therefore the prescribed dose is safe if my child weigh 9.6 kg or more.