The amount of work done in blowing a soap bubble such that its diameter increases from d to D is (T= surface tension of the solution)

(a) $4\mathrm{\pi }\left({\mathrm{D}}^{2}-{\mathrm{d}}^{2}\right)\mathrm{T}$                     (b) $8\mathrm{\pi }\left({\mathrm{D}}^{2}-{\mathrm{d}}^{2}\right)\mathrm{T}$

(c) $\mathrm{\pi }\left({\mathrm{D}}^{2}-{\mathrm{d}}^{2}\right)\mathrm{T}$                        (d) $2\mathrm{\pi }\left({\mathrm{D}}^{2}-{\mathrm{d}}^{2}\right)\mathrm{T}$