how does one calculate the work done by a spherical bubble with radius r in a liquid with a surface tension of T.

I understand for a cavity it is 8pi(r)T, would you just double it to get 16pi(r)T because there are 2 films? here's the math....2(4pi((r)+dr)^2 -4pir^2) for a cavity

mistake, multiplying by 2 in the math is for a bubble and not a cavity >_>