d
\(V = \frac{4}{3}\pi {R^3}\)   \(⇒R = {\left( {\frac{3}{{4\pi }}} \right)^{1/3}}{V^{1/3}}\) 

\(⇒ {R^2} = {\left( {\frac{3}{{4\pi }}} \right)^{2/3}}{V^{2/3}}\)  \(⇒  {R^2} \propto {V^{2/3}}\)

\(W = 8\pi {R^2}T\)   \(⇒  W \propto {R^2} \propto {V^{2/3}}\)

\(\frac{{{W_2}}}{{{W_1}}} = {\left( {\frac{{{V_2}}}{{{V_1}}}} \right)^{2/3}}\) \( = {\left( {\frac{{2V}}{V}} \right)^{2/3}}\)

\( = {(2)^{2/3}} = {(4)^{1/3}} \Rightarrow {W_2} = \sqrt[3]{4}\,W\)