If T is the surface tension of soap solution, the amount of work done in blowing a soap bubble from a diameter D to 2D is
2πD2T
4πD2T
6πD2T
8πD2T
Work done to increase the diameter of bubble from d to D
W=2π(D2−d2)T=2π[(2D)2−(D)2] T=6πD2T