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 $$P_A$$, then the surface tension $$T$$ of the soap solution is

A

$$\frac{P_A(c^3-a^3-b^3)}{4(a^2+b^2-c^2)}$$

B

$$\frac{P_A(a^3+b^3-c^3)}{2(c^2-a^2-b^2)}$$

C

$$\frac{P_A(a^2+b^2-c^2)}{2(c^3-a^3-b^3)}$$

D

$$\frac{P_A(c^2-a^2-b^2)}{4(a+b-c)}$$