Surface tension of a soap bubble is 2.0 x 10-2 Nm-1. Work done to increase the radius of soap bubble from 3.5 cm to 7 cm will be [Take π = 22/7 ]
(a) 0.72 x 10-4 J
(b) 5.76 x 10-4 J
(c) 18.48 x 10-4 J
(d) 9.24 x 10-4 J