Two soap bubbles of radii a and b coalesce to form a single bubble of radius c under isothermal conditions. if the external pressure is a p , then the surface tension (t) of the soap solution is
A. P(c³+a³+b³) / 4 (a² + b²-c)
B. P(c³-a³+b³) / 4 (a² + b²-c)
C. P(c³- 4a³-4b³) / 4 (a² + b²-c)
D. P(c³- 2a³-2b³) / 4 (a² + b²-c)