Example Drug Dosage Problem

Suppose a drug is metabolized and excreted in the body in a manner so 
that it decays with a half-life of 3 hours. The effective dosage range 
for this drug has been found to be fairly broad - from 4 mg per kg of 
body weight to 11 mg per kg of body weight. You have prescribed this 
drug for a 100 kg patient and specified that a dose is to be given 
every 4 hours.

(a) What fraction of the drug in the patient's body will decay between 
each dose?

(b) What periodic dose of the drug must be given in order to ensure that 
the amount of drug in the patient remains within the effective dosage 
range and the amount drops just to the lower end of this range at the 
time of each dose?

(c) What is the loading (bolus) dose to be given to this patient?