Atoms and Nuclei

131l is an isotope of Iodine that β decays to an isotope of Xenon with a half-life of 8 days. A small amount of a serum labelled with 131l is injected into the blood of a person. The activity of the amount of 131I injected was 2.4×105 Becquerel (Bq). It is known that the injected serum will get distributed uniformly in the blood stream in less than half an hour. After 11.5 hours, 2.5 ml of blood is drawn from the person's body, and gives an activity of 115 Bq. The total volume of blood in the person's body, in liters is approximately.(you may use ex≈1+x for |x|<<1 and ln 2≈0.7)