\(\frac{V_{\text {cylinder }}}{V_{\text {sphere }}}=\sqrt{\frac{\left(1+ k ^{2} / R ^{2}\right)_{\text {sphere }}}{\left(1+ k ^{2} / R ^{2}\right)_{\text {cylinder }}}}\)
\(=\sqrt{\frac{1+2 / 5}{1+1 / 2}}=\sqrt{\frac{7}{5} \times \frac{2}{3}}=\sqrt{\frac{14}{15}}\)