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)
