Two soap bubbles of radii `a` and `b` coalesce to form a single bubble of radius `c`. If the external pressure is `P`, find the surface tension of the soap solution.
A. `(P(c^(3)+a^(3)+b^(3)))/(4(a^(2)+b^(2)-c^(2)))`
B. `(P(c^(3)-a^(3)-b^(3)))/(4(a^(2)+b^(2)-c^(2)))`
C. `Pc^(3)-4a^(2)-4b^(2)`
D. `Pc^(3)-2a^(2)-3b^(2)`