Initially the 900μF capacitor is charged to 100 V and the 100μF capacitor is uncharged in Fig. Then switch S2 is closed for time t1, after which it is opened and at the same instant switch S1 is closed for time t2 and then opened. It is now found that 100μF capacitor is charged to 300μF capacitor is charged to 300 V. Find the minimum possible value of the time interval t1 and t2.