A chemotherapeutic agent is initially present at a blood plasma concentration level of 50 μg/100 ml. If after 3 hours...

A chemotherapeutic agent is initially present at a blood plasma concentration level of 50 μg/100 ml. If after 3 hours the concentration level is 20 μg/100 ml, compute the physiological half-life of the drug in hours. You may treat the elimination of the drug as an exponential decay.