Carbamazepine (CBZ) is an antiepileptic drug metabolized to the pharmacologicaly active CBZ-epoxide. CBZ Vd is 1.4 L/kg and half life of 15 hr. After administration of the preformed metabolite CBZ-epoxide it has a Vd of 1.1 L/kg and half life of 7 hr. What will be the experimentally observed terminal half life of CBZ-epoxide after administration of the parent drug CBZ ?