Paula has an acute theophylline poisoning with the substance serum concentration of 9.6 x 10 mcg/L following a period of taking her theophylline tablets q.i.d. instead of b.i.d. Given that the half-life of the substance is 480 mins, how long will it take for her serum concentration to reach a target concentration of 1.2 x 10 mcg/L?

A.16 hrs
B. 8 hrs
C. 24 hrs
D. 32 hrs