IIT JEE Advanced 2009 Paper 2

Two soap bubbles A and B are kept in a closed chamber where the air is maintained at pressure 8 N∕m2. The radii of bubbles A and B are 2 cm and 4 cm, respectively. Surface tension of the soap-water used to make bubbles is 0.04 N/m. Find the ratio nB∕nA, where nA and nB are the number of moles of air in bubbles A and B, respectively. (Neglect the effect of gravity.)