A young male Kallu is brought to the hospital with severe asthma. The pharmacokinetics of theophylline include the following parameters: Vd = 35 L; CL = 48 ml/min; half life is 8 hrs. If an intravenous infusion of theophylline is started at a rate of 0.48 mg/min, how long will it take to reach 93.75% of the final steady state ?