A 29-year-old lady is brought to the clinic with severe asthmatic wheezing. You decide to use intravenous theophylline for treatment. The pharmacokinetics of theophylline include the following average parameters: Vd 32 L; CL 46 mL/min; half-life 8 h. If an intravenous infusion of theophylline is started at a rate of 0.48 mg/min, how long would it take to reach 93.75% of the final steady-state concentration?